Combining with engineering practice, this paper develops the closed-loop control simulation system. The data flow and functional diagram of simulation system are introduced. The single section simulation method and continuous section simulation method are used to simulate the running state of power system, with three different control conditions, including no control, independent control and coordinated control. By the contrast analysis, this paper researches the influence of control condition to system loss, voltage stability margin and tie line reactive power. The simulation results indicate that the coordination among multi-level hierarchical control systems can effectively avoid the control oscillation and reduce the irrational reactive power flow between the higher power system and the lower power system.