For machine tools spindle, noncontact labyrinth seal structure is generally adopted, the cutting fluid is easy to enter the spindle box, causing bearing corrosion.In order to solve this problem, the CNC lathe spindle structure,leakage reason and sealing principle were studied theoretically; a certain type of CNC lathe was taken as the research object, the problems existing in the seal structure of the spindle were analyzed,the labyrinth seal structure was redesigned,and the sealing device at the front end was designed.Improved CNC lathe spindle was formed a triple seal structure by using air shield seal, seal ring seal and labyrinth seal.The using effects show that by using the improved structure, the problem of the spindle seal of the CNC lathe is effectively solved.