The present invention discloses a method for obtaining key management server information, and an intercepting method, system and device, including: in the process of a user equipment registering an IP multimedia subsystem (IMS), storing the KMS information corresponding to the user equipment in a preset IMS core network network element; and when a lawful intercepting device monitors a session initiated by the user equipment, intercepting a session request signaling sent by the user equipment, and obtaining an identification information of the user equipment from the session request signaling, and searching the KMS information corresponding to the user equipment from the preset IMS core network network element according to the identification information of the user equipment. The technical solution of the present invention makes the requirement of lawful intercepting be met without depending on security of the signaling plane when a plurality of KMSs are deployed in the IP multimedia subsystem.