Aiming at different structure of the piston pump, through calculation and MATLAB simulation, research is carried out on the structure size，geometric displacement，flow pulsation etc of the inclined piston and paralleled piston pump under the condition of constant. The result shows: under the same conditions, the flow pulsation of the paralleled pump is slightly better than that of the inclined piston pump. Inclined piston has more advantages compared with the paralleled pump, the displacement of piston is increased，cylinder radial becomes small，and pump has large displacement and small volume. The component force of piston centrifugal has contributed to the piston return, and takes advantage of increased to the oil absorption pressure.