Abstract: A cantilever vertical screw vacuum pump is provided. The vacuum pump has a lubrication system, in the system, an oil splashing sleeve splashes lubricating oil in an oil chamber, the lubricating oil is splashed to the oil guide plates and enters two inner shaft sleeves through oil inlet holes, the lubricating oil is splashed by rotations of lower bearings to lubricate upper bearings and bearing gland oil seal assemblies. A fit between an oil baffle and a lower cover shaft sleeve is a clearance fit, and the oil baffle prevents the lubricating oil from entering a vertical motor. A pressure difference between screw rods is used to output reflux air from a near exhaust end of the screw rods, the reflux air is cooled in a coolant by a reflux cooling pipe, and the cooled reflux air is delivered to the screw rods to reduce an air temperature of the pump chamber.