Aimed at the shortcoming of product of the hydraulic variable piston pump is not mature and the cost is high, a new water hydraulics variable piston pump was designed which was breaking through traditional design concept of the Swash plate hydraulic pump. The pump was integrated with the oil hydraulic components, the simple water hydraulic components and the mechanical mechanism, which could achieve the application requirement of the high pressure large volume.The simulation model of its system was built based on AMESim software, the actual flow curve of the water hydraulics pump was obtained,and an accumulator was set up in the outlet of the pump to control the flow pulsation.The results show that the accumulator can control the flow pulsation effectively and realize the low pulse output of the water pressure pump.