The layout structure of the vacuum pump body determines the overall structure of the pump: 1) vertical structure: the horizontal setting of the inlet and outlet, and the convenient assembly and connection of the pipeline. However, the center of gravity of the pump is high, and its stability is poor at high-speed operation, so this type of pump is mostly used for small pumps; 2) horizontal structure: the air inlet of the pump is on the top, and the air outlet is on the bottom. Sometimes, in order to facilitate the installation and connection of vacuum system pipes, the exhaust port can be connected from the horizontal direction, that is, the inlet and exhaust directions are mutually perpendicular. At this time, the exhaust port can be opened from the left or right direction. In addition to connecting one end of the exhaust pipe, the other end is blocked or connected with the bypass valve. The pump has low center of gravity and good stability at high speed. Generally, large and medium-sized pumps use this structure. The two rotor shafts of the pump are installed vertically with the horizontal plane. The assembly clearance of the structure is easy to control, the rotor is easy to assemble and the pump occupies a small area. However, the center of gravity of the pump is high and the gear is inconvenient to be disassembled, and the lubricating mechanism is relatively complex.