The present invention discloses a method and a system for implementing single radio voice call continuity (SRVCC), and said method includes: an ALG sending number information and/or identifier information if the ALG to a SCAS via a signaling message; said SCAS judging whether the number information and/or identifier information of the ALG are identical with the last used REFER number information or not, and if not, said SCAS notifying a PS or CS network control entity of the number information and/or identifier information of the ALG; alternatively, said SCAS notifying the PS or CS network control entity of the number and/or identifier information of the ALG. The present invention implements to dynamically select the ALG as a REFER operation entity to implement SRVCC, and solves the problem that a REFER request cannot be sent to an appropriate ALG since this ALG cannot be dynamically determined.