Compared with fixed displacement hydraulic motor system, variable displacement hydraulic motor system has a significant improvement in peak flow consumption, overall efficiency and equipment size, and has the advantage of fast response. It can meet the demand of high power and large inertia load. Based on the nonlinearity characteristic of the hydraulic servo system and the time variability of the load parameters, the control strategy of the variable displacement hydraulic motor control system is studied. The speed control and the motion position control method are analyzed by AMESim modeling and simulation. Conventional PID controller can not adjust control parameters according to load changes in real time, which can cause instability due to speed fluctuation. Therefore, we utilize the fuzzy PID control model of AMESim and Simulink in Matlab to model and simulate the servo system. Simulation results show that compared with the conventional PID control, fuzzy PID control has a significant advantage in terms of response speed and stability performance.