Method for triggering routing of IMS (IP multimedia subsystem) domain in CS (circuit switched) domain, agent device, AS (application server) in IMS domain and SCP (service control point)

The invention discloses a method for triggering routing of an IMS (IP multimedia subsystem) domain in a CS (circuit switched) domain, an agent device, an AS (application server) in the IMS domain and a CP (service control point). The method comprises the following steps: a GSCP/AS (gateway service control point/application server) agent device receiving a request for querying called party anchoring information sent by the SCP; and the GSCP/AS agent device feeding back the called party anchoring information acquired form the AS in the IMS domain to the SCP, wherein the GSCP/AS agent device supports a dual cross-domain interface crossing the CS domain and the IMS domain, and the GSCP/AS agent device and the AS in the IMS domain are synchronized in real time to acquire and update IMS domain service information and the anchoring information of the corresponding subscriber in real time. Through the adoption of the method disclosed by the invention, the GSCP/AS agent device crossing dual domains is provided for acquiring IMS core network related service information; the routing is optimized and released in reference to a certain anchoring routing rule, so that the calling connection can be directly established in the CS domain by the SCP when the calling is unnecessary to route to the IMS domain, and a roundabout speech channel can be avoided,