Radial piston pump can be divided into valve distribution and axial distribution of two major categories. Valve-Flow Radial plunger pump has disadvantages of high failure rate and low efficiency. The axial-flow radial plunger pump developed by the international 70 and 80 has overcome the insufficiency of the radial plunger pump of valve distribution. Because of the characteristics of the radial pump structure, the axial piston pump has the advantages of high impact, long life and higher control precision than the axial plunger pump. Variable stroke Short pump variable is in variable plunger and limit plunger action, change the stator eccentricity, and the maximum eccentricity is 5-9mm (according to displacement size), variable travel is very short. The variable mechanism is designed for high pressure operation and controlled by the control valve. So the pump response speed is fast. The radial structure design overcomes the problem of eccentric abrasion of the slide shoe of axial piston pump. So that its ability to resist impact greatly improved.