Dry screw vacuum pump is the use of a pair of screw, in the pump shell for synchronous high-speed reverse rotation to produce suction and exhaust effect of a vacuum extraction equipment. Dry screw vacuum pump working principle is: use mutual meshing gear synchronous reverse rotation without contact left screw with the right screw for high-speed rotation, using the pump casing and pitch propeller spiral groove divided into multiple space, the formation of multiple level, gas in each groove equal to transmit motion, but without compression, only the screw end helical structure of gas compression, eventually form a vacuum.