It is mainly composed of pump cylinder 4, piston 5, suction valve 3 and discharge valve 8. The piston 5 is connected with the live cold rod 6, which can be driven by the prime mover through the transmission mechanism to make a linear reciprocating movement in the pump cylinder. The cylinder 4 can be connected to the suction pipe 2 and the discharge pipe 9 through the suction valve 3 and the discharge valve 8 respectively. The suction pipe goes deep below the liquid surface to be transported, the lower end is equipped with a suction filter 1, and the discharge pipe 9 leads directly to the place where water is needed. When the piston moves from left to right, the volume in the pump cylinder 4 increases and the pressure decreases. At this time, the atmospheric pressure below the suction valve will overcome the pressure acting on the suction valve and push the suction valve open so that the suction pipe communicates with the pump cylinder, and the pressure in the suction pipe decreases. Therefore, the liquid level in the suction pipe is reduced. Will rise. When the piston moves from right to left to start the discharge stroke, the suction valve 3 is closed under the action of its own weight, the spring tension on the valve and the increasing air pressure in the pump cylinder. Thereafter, the air in the pump cylinder will be compressed by the piston moving to the left to reach a pressure sufficient to open the discharge valve. When the discharge valve is opened, air is squeezed out of the discharge pipe until the piston reaches the extreme left position.

The piston continuously reciprocates, the gas in the suction pipe will be continuously discharged to the discharge pipe, and the liquid in the suction pipe will rise after each suction stroke of the piston, until the liquid will be full at the end of suction. Pump cylinder, and discharge it from the discharge pipe during the discharge stroke, so that the pump starts to work normally.