The embodiment of the invention provides a user authentication method, an intelligent gateway and an authentication server. In the embodiment of the invention, after receiving a first service access request sent by a user through a terminal, the intelligent gateway sends a first user authentication request including a gateway identifier and the service identifier of a target service to the authentication server; the authentication server generates an authentication token according to the gateway identifier and the service identifier, and feeds back the authentication token to the intelligent gateway; the intelligent gateway sends a second service access request carrying the authentication token, the gateway identifier, the service identifier and user login information to a third-party service system, so that the third-party service system sends a second user authentication request to the authentication server; the authentication server performs authentication processing of the user, and feeds back the authority information that the user accesses the target service to the third-party service system; thereby, the authentication server uniformly authenticates users initiating third-party service access requests; and thus, the process that the users access the third-party service system is relatively convenient and rapid.