Method for supporting multi-call when interworking between UTRAN and synchronous core network in IMT-2000 system

A method for supporting a multi-call in an IMT-2000 system providing a plurality of services including a voice communication service, a moving picture service and a radio internet service, wherein the IMT-2000 system includes one or more mobile stations, one or more radio networks and one or more core networks includes the steps of: in response to a call request of the mobile station, transmitting an origination message to the radio network; generating a CM service request message based on the origination message and transmitting the CM service request message to the core network; determining whether the call request is an initial call request or an additional call request based on the CM service request message, wherein the additional call request means a request of an additional traffic channel for using other service; generating one or more traffic channels for the mobile station; and storing a first identity for the mobile station and a second identity for an assigned traffic channel in a storage unit.