Taking a certain type of closed high-pressure piston pump as an object, a three-dimensional models of the port plate and the cylinder part were established, the mesh division and the calculation model selection were carried out by using PumpLinx software, and the full flow field simulation calculation of the closed piston pump with V-groove port structure was carried out. Its distribution cavitation characteristics were analyzed and compared with the cavitation damage on the cylinder surface after the durability test. The mechanism of cavitation generation and cavitation damage of the closed piston pump with V-groove distribution structure was obtained.