Aiming at the demand of dynamic response and followup of rail pressure control of high pressure common rail diesel engine in the whole operating range, the control strategy of the rail pressure system was proposed by analyzing the rail pressure working principle, and a PID rail pressure control algorithm with dynamic grading coefficient was designed. The control algorithm was improved in many ways, including rail pressure acquisition, feedforward control, PID control and IMV valve drive. The improved rail pressure control algorithm was modeled by using the model-based design method and Simulink software. The code of the rail pressure control algorithm was integrated into the engine controller by using the automatic code generation technology, and the engine bench test was carried out. The test results show that the rail pressure control algorithm has good following performance and response speed, and the rail pressure control is relatively stable. In steady condition, the difference between the command rail pressure and the feedback rail pressure is less than 2.0 MPa; in dynamic condition, the difference between the command rail pressure and the feedback rail pressure is less than 3.0 MPa.