Satellite simulated system is a very important sub system of satellite payload ground comprehensive testing system which tests the satellite payload's order and telemetering before delivering the payload to satellite. For all kinds of satellite simulated system, a new implementation which used an improved Finite State Machine ( FSM) model can make the whole system modules clear, reduce the coupling between modules, improve the modules' reusability, enhance productivity, and make the research and development of the whole system easier. The engineering applications' experimental results show that the implementation of an improved FSM model can make the satellite simulated system stable and reliable.