Roots vacuum pump is also known as the mechanical booster which is a positive displacement type pump. It is one of the special pumps which can reach middle, high vacuum rang. Its work principle is similar to the Root fan. Both of them used a pair of rotors, whose shape looks like 8, to achieve the suction and discharge process. According to the technical that the plenty of vapor and solvent is required to pump in the mechanical, pharmacy areas, we have improved the seal type of the bearing housing and gear box of the ZBK series Roots pump to reduce the emulsification of the pump oil efficiently and make the Roots pump more suitable to assemble with the water ring vacuum pump to suction more vapor and solvent.