Flow ripple is the main cause of the noise of the piston pump, and the flow ripple will be transmitted to other components of the hydraulic system through pipelines, causing its vibration and noise, so reducing the flow ripple of the piston pump has become an important issue of research.Traditionally, the way reducing the flow ripple is to process the triangular groove at the front of the kidney groove of the valve plate, but this way is more sensitive to the operating conditions, and can not reduce the ripple well when the speed and pressure change. Another way to reduce flow ripple was verified by PumpLinx simulation software. This way was to set a pre-compression chamber at the front of the triangular groove of the valve plate. The simulation results show that when the speed and outlet pressure change, the pre-compression chamber can reduce the flow ripple better.