The working principle of the water ring vacuum pump: the impeller of the water ring vacuum pump blade is eccentrically mounted in the cylindrical pump casing. A certain amount of water is injected into the pump. When the impeller rotates, the water is thrown to the pump casing to form a water ring, and the inner surface of the ring is tangent to the impeller hub. Because the pump casing and the impeller are not concentric, the air inlet space 4 between the right half hub and the water ring gradually expands, thereby forming a vacuum, so that the gas enters the air inlet space in the pump through the air inlet pipe. Then the gas enters the left half, and the pressure is increased as the volume between the hub rings is gradually compressed, so the gas is discharged to the outside of the pump through the exhaust space and the exhaust pipe.