Abstract: Based on the simulation flat-SIMULINK, the simulation model of Power Regulating System(PRS) of China Advanced Research Reactor is built up. By computing the reactor power response to reactivity disturb, the information on the system stability, the regulating quality, and the effect of parts on the whole close loop system can be (obtained). System simulation indicates that the close loop system not only is capable of overcoming the reactivity disturb, but also has good fixed value following characteristic.