a method for realizing the synchronous authentication among the different authentication control devices is provided . the user accesses the network and initiates the authentication by the slave authentication control device . then the master authentication control device obtains the authentication information of the user from the slave authentication control device and transmits it to the master authentication server of the master authentication control device . finally , the master authentication server performs the authentication process to the user according to the authentication information of the user . therefore the accessing user can obtain the network authority of a plurality of service providers with only one logging on in the network in which a plurality of service providers are interconnected . the present invention facilitates the access to the network for the user and can assure that each service provider can control and manage the accessing user efficiently and thereby protects the benefit of the service providers .