A method and system for implementing large capacity calls by using the H.323 protocol stack are provided in the present invention. The method comprises: a plurality of protocol stacks are deployed in a multi-point control unit; an IP address of a third protocol stack is pre-configured as a uniform IP address of the multi-point control unit, wherein the IP address acts as an incoming address when the multi-point control unit is called, and the third protocol stack is used to perform the H.225 signaling interaction with the opposite end when the multi-point control unit is a called party; when the multi-point control unit is a calling party, a first protocol stack, the number of processable calls of which does not exceed a limit number, is selected to perform the H.225 signaling interaction with the opposite end, and a second protocol stack, the number of processable calls of which does not exceed a limit number, is selected to perform the H.245 signaling interaction with the opposite end; when the multi-point control unit is a called party, a fourth protocol stack, the number of processable calls of which does not exceed a limit number, is selected to perform the H.245 signaling interaction with the opposite end. In the present invention, the H.245 messages from different ends are distributed to a plurality of protocol stacks for processing, which thereby improves the processing efficiency.