the present invention provides an array substrate and a manufacturing method thereof and a display device , belonging to the field of display technology and solving the problems that the display quality is reduced and the normal watching is affected due to alignment shifting during alignment in an existing thin film transistor liquid crystal display . the array substrate of the present invention includes a plurality of sub - pixel units , wherein a plurality of light forming units corresponding to the sub - pixel units are arranged on a light - exiting surface of the array substrate , and each of the light forming unit is configured to form light of a color of the sub - pixel units corresponding thereto . when the array substrate of the present invention is applied to the display device , the display quality of the display device may be improved .