System for hand off using multi party service in mobile communication system and method thereof

A handoff system and method using an MPTY (multiparty) service in a mobile communication system. When a terminal senses that it is located at the boundary of a WCDMA during a WCDMA communication service, it transitions to a first state. In the first state, the terminal requests an MPTY service to a BS in a CDMA network. If the strength of a first current WCDMA signal is less than a predetermined first threshold, the terminal transitions to a second state. In the second state, the terminal requests an available MPTY call to be maintained. If the strength of a second current WCDMA signal is less than a predetermined second threshold, the terminal transitions to a third state. Then the terminal establishes a CDMA call using the maintained MPTY call in the third state. If the strength of a third current WCDMA signal is less than a predetermined third threshold, the terminal ends the WCDAM call.