A method for implementing an IP Multimedia Subsystem (IMS) registration, includes: a Home Subscriber Server (HSS) recording a current registration state of a User Equipment (UE) in response to receiving a Multimedia Authentication Request (MAR) initiated by a Service Call Session Control Function (S-CSCF) selected for the UE when a first Register request is sent by the UE; in response to receiving a second Register request initiated by an Interrogating Call Session Control Function (I-CSCF), the HSS sends the S-CSCF Name to the I-CSCF when the current registration state of the UE is an assigned S-CSCF state. By the scheme, a same S-CSCF is ensured to be used in the two User Authentication Request/User Authentication Answer (UAR/UAA) procedures of the initial IMS registration procedure, and the initial IMS registration of the UE is implemented successfully.