A method and a system for calling a traditional circuit switched domain network user by a packet core network. The method includes: after receiving a request message from a call session control unit, a media gateway control unit sends the call session control unit a first call progress message carrying a preset prompt tone indicating please wait; the media gateway control unit sends an initial address message to the traditional circuit switched domain network and start a preset timer; if the timer expires and the traditional circuit switched domain network does not respond, the media gateway control unit sends the call session control unit a second call progress message carrying a preset prompt tone indicating that the other party is temporarily unaccessible, and the media gateway control unit proceeds according to a preset policy. Resource waste due to waiting is avoided and better user friendliness of a service is provided.