Reciprocating vacuum pump is also called piston vacuum pump, which is composed of crankshaft, piston, cylinder, frame, intake and exhaust valve seat. The crankshaft is driven by the motor to rotate, so that the piston moves up and down in the cylinder. The gas in and out of the intake and exhaust valves will pump out a fixed volume of gas and make it empty. Reciprocating vacuum pump is the oldest vacuum pump, its advantage is that the gas does not need to contact with other liquids, but it also has the disadvantages of low efficiency, high noise, oil mist, and many vulnerable parts. In practical application, many fields have been replaced by liquid ring vacuum pump. Compared with reciprocating vacuum pump, liquid ring vacuum pump does not need vacuum pump oil for lubrication, and its structure is relatively simple, and its maintenance cost is relatively low.