The main bearing used in high-speed spindle unit are angular contact ball bearings, bearings, water-based magnetic levitation of dynamic and static pressure bearing, air static pressure bearing, etc.Due to expensive, magnetic levitating bearing control system is complex, fever problem difficult to solve, so it cannot be applied in high speed spindle unit.Water hydrostatic bearing is the present domestic is one of the hot research topic, it is the use of water has the characteristics of large heat capacity, bearing temperature rise smaller, part solves the common problems, dynamic and static pressure bearing heating, mainly used in the situation of low speed and heavy loading.Air static pressure bearing low radial stiffness and good impact, but the performance is good, is generally used in ultra-high speed, light load, precision spindle.Angular contact ball bearing dn value below 2.0 x 106 application in high-speed spindle unit, whether it is a speed limit, the bearing capacity, stiffness, precision and so on various aspects all can well meet the requirements, and has set up a standardized price is low, 90% of the spindle components are using this type of bearings.