reference can be made to fig1 , which is a schematic flow diagram of a method for viewing a presentation document in a mobile device according to the present invention . the method for viewing a presentation document in a mobile device includes the following steps : step s 101 : determining an orientation of a screen according to a sensing signal from a gravity sensor . the method for viewing a presentation document in a mobile device according to the present invention is started when a user chooses to open a presentation document with a document processing software ( such as wps ) or the like . at first , the sensing signal from the gravity sensor of the mobile device is obtained , according to which whether the current orientation of the screen of the mobile device is portrait or landscape is determined . since there are relatively well - established methods in the prior art for determining the orientation of the screen according to the sensing signal from a gravity sensor of a mobile device , the specific method for performing this step in the present invention is not listed herein . step s 102 : displaying the thumbnails of slides in the presentation document at lower part of the screen in a horizontal arrangement when the orientation of the screen is portrait . when the orientation of the screen is determined to be portrait , i . e . the viewing angle of a user typically becomes a portrait orientation , the thumbnails of the slides contained in the presentation document is displayed at the lower part of the screen in a horizontal arrangement . particularly , since the main body of the slide is displayed , generally in the middle of the screen , at the same time when the thumbnails are displayed , and the size of the main body of the slide displayed is much larger than that of the thumbnails , the main body of the slide can be displayed in the middle of the screen or at the upper part of the screen , and the thumbnails is displayed at a position at the lower part of the screen outside of the main body of the slide . since the orientation of the screen is portrait and the thumbnails are displayed at the lower part of the screen , there is still a large spare space in the middle of the screen and at the upper part of the screen , so that the displaying of the thumbnails will not occupy the display position of the main body of the slide of the presentation document , and the user can perform display switching by clicking a thumbnail displayed at the lower part . step s 103 : displaying the slide thumbnails of the presentation document at the left part or the right part of the screen in a vertical arrangement when the orientation of the screen is landscape . when the orientation of the screen is determined to be landscape , i . e . the viewing angle of a user typically becomes a landscape orientation , the thumbnails of the slides contained in the presentation document is displayed at the left part or the right part of the screen in a vertical arrangement . similarly , the main body of a slide can be displayed in the middle of the screen , and the thumbnails are displayed at the left part or the right part of the screen at a position outside of the main body of the slide . since the orientation of the screen is landscape and the thumbnails are displayed at the left part or the right part of the screen , there is still a large spare space in the middle of the screen , so that the display of the thumbnails does not occupy the display position of the slide main body of the presentation document , and the user can perform display switching by clicking the thumbnails displayed at the left part or the right part . the method for viewing a presentation document in a mobile device according to the present invention determines the orientation of the screen according to the sensing signal from a gravity sensor when a user opens a presentation document ; displays the thumbnails of the slides in the presentation document at the lower part of the screen in a horizontal arrangement when the orientation of the screen is portrait ; and displays the thumbnails of the slides of the presentation document at the left part or the right part of the screen in a vertical arrangement when the orientation of the screen is landscape . therefore , it is possible to display the slide thumbnails of the presentation document in a more suitable manner according to different orientations of the screen , facilitating the viewing and operating of the presentation document by a user . the display mode in the method according to the present invention is more conformable to the psychological expectation of the user , resulting in better user experience . in an embodiment , when the orientation of the screen is portrait , the switching mode of the slides is further set as left / right sliding switching ; and when the orientation of the screen is landscape , the switching mode of the slides is further set as up / down sliding switching . when the orientation of the screen is portrait , the slide thumbnails are displayed at the lower part of the screen in a horizontal arrangement , and the slide can be displayed in the middle of the screen or at the upper part of the screen . therefore , the switching mode of the slides can be set as left / right sliding switching , so that the displaying of the slide main body will not be blocked when the sliding switching is performed . similarly , when the orientation of the screen is landscape , the slide thumbnails are displayed at the left part or the right part of the screen in a vertical arrangement . therefore , the switching mode of the slides can be set as up / down sliding switching , so that the display of the slide main body will not be blocked when the sliding switching is performed . in another embodiment , when the orientation of the screen is portrait , the display mode of the slides is further switched to an imagery mode ; and when the orientation of the screen is landscape , the display mode of the slides is further switched to a scenery mode . with the above - mentioned method , when the orientation of the screen of a mobile device changes , a self - adaptive switching of the display mode of the slides is further achieved for displaying the slides to users in a more suitable display mode , thus further improving the user experience . reference can be made to fig2 , which is a schematic structure diagram of a system for viewing a presentation document in a mobile device according to the present invention . the system for viewing a presentation document in a mobile device includes : an orientation sensing module 11 and a thumbnail display switching module 12 . the orientation sensing module 11 is used to determine the orientation of a screen according to the sensing signal from a gravity sensor ; and the thumbnail display switching module 12 is used to display the slide thumbnails of the presentation document at the lower part of the screen in a horizontal arrangement when the orientation of the screen is portrait , and to display the slide thumbnails of the presentation document at the left part or the right part of the screen in a vertical arrangement when the orientation of the screen is landscape . the system for viewing a presentation document in a mobile device according to the present invention is started when a user chooses to open a presentation document with a document processing software ( such as wps ) or the like . at first , the orientation sensing module 11 obtains the sensing signal from the gravity sensor of the mobile device , and determines whether the current orientation of the screen of the mobile device is portrait or landscape according to the sensing signal . since there are relatively well - established methods in the prior art for determining the orientation of the screen according to the sensing signal from the gravity sensor of a mobile device , the specific determining methods are not listed herein . when the orientation of the screen is determined to be portrait , i . e . the viewing angle of a user typically becomes a portrait orientation , the thumbnail display switching module 12 displays the thumbnails of the slides contained in the presentation document at the lower part of the screen in a horizontal arrangement . particularly , since the main body of the slide is displayed , generally in the middle of the screen , at the time when the thumbnails are displayed , and the size of the slide main body displayed is much larger than that of the thumbnail , the thumbnail display switching module 12 can display the main body of the slide in the middle of the screen or at the upper part of the screen , and the thumbnails are displayed at the lower part of the screen at a position outside of the slide main body . since the orientation of the screen is portrait , and the thumbnails are displayed at the lower part of the screen , there is still a large spare space in the middle of the screen and at the upper part of the screen , so that the display of the thumbnails does not occupy the display position of the slide main body of the presentation document , and a user can perform display switching by clicking the thumbnails displayed at the lower part . when the orientation of the screen is determined to be portrait , i . e . the viewing angle of a user typically becomes a portrait orientation , the thumbnail display switching module 12 displays the thumbnails of the slides contained in the presentation document at the left part or the right part of the screen in a vertical arrangement . similarly , the thumbnail display switching module 12 can display the main body of the slide in the middle of the screen , and the thumbnails are displayed at the left part or the right part of the screen at a position outside of the slide main body . since the orientation of the screen is landscape and the thumbnails are displayed at the left part or the right part of the screen , there is still a large spare space in the middle of the screen , so that the display of the thumbnails does not occupy the display position of the slide main body of the presentation document , and a user can perform display switching by clicking the thumbnails displayed at the left part or the right part . in the system for viewing a presentation document in a mobile device according to the present invention , the orientation sensing module determines the orientation of the screen according to the sensing signal from a gravity sensor when a user opens a presentation document ; and the thumbnail display switching module displays the slide thumbnails of the presentation document at the lower part of the screen in a horizontal arrangement when the orientation of the screen is portrait , and displays the slide thumbnails of the presentation document at the left part or the right part of the screen in a vertical arrangement when the orientation of the screen is landscape . therefore , it is possible to display the thumbnails in a more suitable manner according to different orientation of the screen , facilitating the viewing and operating of the presentation document by a user . the display mode in the method according to the present invention is more conformable to the psychological expectation of the user , resulting in better user experience . reference can be made to fig3 , which is a schematic structure diagram of an embodiment of the system for viewing a presentation document in a mobile device according to the present invention . in an embodiment , the system for viewing a presentation document in a mobile device according to the present invention further includes a sliding switching module for the slides 13 , which is used to set the switching mode of the slides as left / right sliding switching when the orientation of the screen is portrait ; and to set the switching mode of the slides as up / down sliding switching when the orientation of the screen is landscape . when the orientation of the screen is portrait , the slide thumbnails are displayed at the lower part of the screen in a horizontal arrangement , and the slide is displayed in the middle of the screen or at the upper part of the screen . therefore , the sliding switching module for the slides 13 sets the switching mode of the slides as left / right sliding switching , so that the display of the slide main body will not be blocked when the sliding switching is performed . similarly , when the orientation of the screen is landscape , the slide thumbnails are displayed at the left part or the right part of the screen in a vertical arrangement . the switching mode of the slides can be set as up / down sliding switching , so that the display of the slide main body will not be blocked when the sliding switching is performed . reference can be made to fig4 , which is a schematic structure diagram of another embodiment of the system for viewing a presentation document in a mobile device according to the present invention . in another embodiment , the system for viewing a presentation document in a mobile device according to the present invention further includes a display mode switching module 14 , which is used to switch the display mode of the slides to an imagery mode when the orientation of the screen is portrait ; and to switch the display mode of the slides to a scenery mode when the orientation of the screen is landscape . when the orientation of the screen of a mobile device changes , a self - adaptive switching of the display modes for the slides is further achieved by the display mode switching module 14 for displaying the slides to users in a more suitable display mode , thus further improving the user experience . the embodiments of the present invention described above are not intended to limit the scope of the present invention . any modifications , equivalent substitutions , improvements or the like made within the spirit and principle of the present invention shall be included in the protection scope of the claims in the present invention .