Taking a high-speed axial piston pump as the research object, a CFD numerical simulation model with cavitation module was built. Based on the simulation model, the cavitation of the piston pump during the rotation process was analyzed. The results show that the cavitation mainly occurs in the piston cavity, and the main reasons for the cavitation are insufficient liquid filling rate and too large jet angle. Aiming at the cavitation mechanism, the opening angle of the valve plate was optimized by combining simulation data with theoretical data. According to the flow field, a valve plate structure with a certain slope at both ends was proposed and optimized. After the optimization of valve plate opening angle and structure, the overall cavitation degree in the piston is reduced by 74.2%, which has obvious inhibition effect on cavitation.