Abstract: This energy-saving, water injection booster pump was designed in view of the problems like high energy consumption of water injection booster equipment used in oilfields and water injection pressure not being able to be properly adjusted. This pump controls the right and left travel of the piston by mechanical direction valve, hence controlling the liquid flow inside the pump and boosting the liquid flow through double-acting piston booster pump. Through analysis of stress on piston structure, the movement of piston is divided into two stages. The first stage is accelerating stage and the second stage is constant speed stage. The piston movement speed, movement period and effective power were calculated. The ANSYS software was used to conduct finite element simulation calculation of piston cylinder and the piston, which showed that its structure strength can meet the specifications. This pump was used to boost two high pressure wells in Shengli Oilfield, and the booster was 1.5 MPa, which could meet the requirement of injection pressure and daily injection volume and accomplish the task of injection increase. The pressure and flowrate at low pressure outlet could meet the requirement of water injection at one or two low pressure wellhead.