The plunger is mounted in the plunger pump cylinder and evenly distributed along the axial circumference. The end of the plunger is provided with a shoe, which is pressed against the swash plate by the spring through the return stroke disk. At the same time, the cylinder is pressed against the fixed counterplate under spring force and working oil pressure. The port plate has two waist-shaped windows and one, with a pump housing connected to the suction port, said the oil into the window; the other shell of the oil drain connected, said the oil drain window. The width between the distribution window should be greater than the width of the bottom of the cylinder port to prevent collusion between high and low pressure chamber. Axial hydraulic piston pump at work, the main drive shaft to drive the cylinder rotation. As the swash plate has a tilt angle, the plunger reciprocates in the plunger hole of the cylinder body when the plunger pump cylinder rotates, thus completing the oil absorption and pressure oiling process of the hydraulic pump.