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Aiming at the problems of cavitation and positive and negative overshoot of pressure，caused by closed compression and closed expansion in the switching process of oil suction and discharge of axial piston pump, leading to flow pulsation, a 2D (twodimensional) pump was designed. The rotation of piston was used to distribute flow, and the distribution grooves of the piston were evenly distributed, which can eliminate the independent distribution mechanism and the effects of closed compression and closed expansion. In addition, two pistons in series were used to eliminate the structural flow pulsation caused by the motion law of piston. In order to further study the mechanism of flow fluctuation, mathematical models of instantaneous flow and pressure characteristics were established, the relationships between the structural parameters and the pressure in the cavity and the outlet flow were analyzed. It was concluded that the distribution area was the main factor affecting the flow fluctuation. Finally, the test bed was built, the prototype was made and tested. The experimental results showed that the volume efficiency of the prototype can reach 96% and the flow fluctuation was as low as 6.3%. It showed that the structure of the 2D pump can achieve high volume efficiency, and the flow fluctuation can be reduced by rotating flow distribution and double piston series connection. Damping groove in distribution windows also reduced flow ripple.