The invention discloses a design and optimization method for distributed IMS (IP Multimedia Subsystem) architecture based on load balance. The method comprises the following steps: collection and update of load information based on IMX nodes: sending messages to local resource controllers of all the IMX nodes by a global resource controller, and returning collected load parameters of all the IMX nodes to all the local resource controllers; and resource allocation: after the collection and update of the load information based on the nodes, reallocating loads through the IMX nodes, namely, finishing establishment and transmission of a session by using all resources. In the method, a load sharing mechanism in a distributed system is put forward, and a strategy which is most suitable for a distributed IMS implementation demand is provided through analysis of a design space and approval of certain mechanisms. The load sharing mechanism is a lightweight mechanism with minimum overhead. Through the research of the method, a basis and guidance are provided for specific implementation of further improvement on load sharing.