The present invention provides a message processing method, apparatus based on the SIP Protocol and an IP communication system, wherein the method comprises: a step for processing messages from a core network, for using a SIP proxy server as a uniform access interface for SIP messages from the core network to judge and distribute the received SIP messages to corresponding application servers for processing; a step for processing messages from the application servers, for using the SIP proxy server as a uniform access interface for SIP messages from the application servers to distribute, according to instructions from the application servers, the received SIP messages to corresponding core network device for processing. Thus, with the method and system of the present invention, when the processing capability of one application server is not enough, the processing capability of the application server could be improved by expanding the number of the application servers without any need to perform modification of the configuration by the core network device.