The working principle of rotary vane vacuum pump is: the front and rear stage rotors with rotary vane are installed eccentrically in the cylindrical front and rear stage cylinders. When the rotor rotates at a high speed, the rotary vane which is installed in the rotor groove and free to move is forced outward due to centrifugal force and spring force, and its top and the inner wall of the cylinder are close to each other so that the imports and exports on the cylinder are isolated by them.