Abstract: Based on the pressure control system of the pressurizer with digital regulator, and according to different dynamic characteristics of the pressurizer pressure rising or reducing, a control system using a digital regulator with two sets of parameters used in control pressure of pressurizer is proposed in this paper. The design of SAMA Diagram of Control Strategy with automatic switching function was given and two sets of PI parameters of digital regulators were tuned in SIMULINK. The results verify that the design could better recover the pressure to the set point, thus the design improves the security of operation in nuclear power plants.