This kind of pumps has the specialties as follows: 1)If there isn’t vapor to generate, You can turn off the adulterating-gas valve to increase the vacuum degree. 2) The improvement of the adulterating-gas valve can make the pump have adequate adulterating gas amount as pumping vapor, so the cogulable gas can be eliminated timely and the pump oil can be prevented from being lactic. 3) It is installed with the device that can make oil revival in which the oil,water and vapor can be frozen and separated, so the oil can be cleaned in time, and be used repeatedly,therefore, the working time of the pump is prolonged and the working reliability is increased.