A user token management system in a client device on a network comprises an obtaining module, a web controller and a processing module. The obtaining module obtains a user token from a database in response to a retrieving request for retrieving authorization of a web service provider on the network. The web controller transmits an authenticating request for authenticating the user token to the web service provider and receives an authentication result authenticating the user token. The processing module deletes the user token from the database when that user token is not authenticated by the web service provider.