The invention discloses an SIP (Session Initiation Protocol) protocol stack load balancing system and method in a telecommunication network IMS (IP Multimedia Subsystem). A solution of a cluster-typeSIP protocol stack is provided, and a plurality of processing clusters such as a transmission layer processing cluster, a transaction layer processing cluster and a transaction user layer processing cluster are introduced. According to the invention, the transmission layer, the transaction layer and the transaction user layer are deployed according to a multi-module and multi-node cluster mode, sothat the functional coupling degree among the transmission layer, the transaction layer and the transaction user layer can be reduced functionally, and complete processing of the SIP protocol can berealized; on the aspect of reliability, multi-node redundant backup is carried out between the same modules, and a single-point fault is avoided; from the aspect of performance, the call processing performance and reliability of the single-node SIP protocol stack are greatly improved, and the influence on an existing network is reduced to the minimum.