A method for realizing an authentication center (AC) and an authentication system are disclosed. The method comprises: a UE sends an authentication request to an AC and applies for temporary authentication information, the AC assigns a first authentication random code to the UE, then the UE calculates a first response code and sends it to the AC, the AC assigns the temporary authentication information to the UE after authentication and authorization; the UE sends a login request to the application system (AS) which assigns a second authentication random code to the UE, and the UE uses it and the temporary authentication information to calculate a second response code, and sends this code to the AS; the AS sends the second response code to the AC for authentication and authorization; the AC returns the authentication result to the AS which in turn returns the authentication result to the UE.