Abstract: The reactor power control system is the core of the reactor control system in the nuclear power plant. Based on an experimental reactor as the research object, the simulation model of the power regulating system was built, and the power regulator in the nuclear power plant by using the frequency domain method was designed. Compared with the traditional PID control structure, this method has the obvious advantages, such as the clear and simple design steps, the wider industrial control requirements, etc. The simulation results show that this method has the better tracking control performance, strong robustness, and can eliminate uncertain interference. It is also practically significant for the reactor participating in the peak shaving of the power grid.