Abstract: The overall control tactics for the automatic clod start-up of nuclear power plant is discussed in the paper. Then, different control methods are designed to realize the auto-control of the primary loop coolant temperature, the levels of the temperature, the pressure and the water of the pressurizer, and the steam pressure of SG, respectively, in different phases. The control effects are demonstrated using a comprehensive nuclear power plant control simulation platform based on the RELAP5 and SIMULINK. The simulation results show that with the designed control methods, the automatic control of the nuclear power plant start-up from cold shutdown can be realized, and the requirements of operating regulations and safety can be satisfied.