Multi-target tracking accuracy is an important indicator of airborne Infrared Search and Track (IRST) system, and the experimental verification of it under test flight conditions is not only costly but also difficult. Based on the features of multi-target tracking of IRST system, a semi-physical simulation system was designed for multi-target tracking accuracy testing. The system consists of a target simulation system, a dynamic excitation system, a system controller, a data acquisition processor and other components. By connecting to a transmission network composed of high-speed Ethernet and avionics busses, it can carry out dynamic testing of multi-target tracking accuracy under laboratory conditions. This paper describes the system composition, function and detailed design of the key target simulator, and the working principle of the multi-target tracking accuracy testing is also given.