Abstract: Based on MATLAB/Simulink platform, all the related models in reactor power regulation system were built, and the range of controller parameter to keep system steady was obtained by calculating the simplified system model with discrete control theory. The simulation analysis was conducted with integrated system model in Simulink platform to determine the best sample time and the corresponding optimized PID controller parameter. The simulation results show that the digital reactor power regulation system is able to keep reactor power stable and the dynamic characteristic of the system is excellent.