A method and a device for providing services for a user are provided. The method includes receiving, by an interrogating call session control function (I-CSCF), a failure response returned by a first serving call session control function (S-CSCF) after the I-CSCF selects the first S-CSCF for the user according to a capability set of an S-CSCF returned by a home subscriber server (HSS) and forwards a service request to the first S-CSCF; obtaining, by the I-CSCF, information of a second S-CSCF, and forwarding the service request from the user to the second S-CSCF. Therefore, when multiple identities of the user simultaneously generate unregistered services, when they generate registration requests at the time of generating unregistered services, or when they simultaneously generate registration requests, the I-CSCF forwards the service request from the user to a corresponding S-CSCF for processing, thus enabling a network to normally provide services for the user.