Slewing bearing is a bearing that can accommodate large axial load, radial load and overturning moment. Slewing bearings generally have installation holes, inner teeth, outside teeth, lubricants holes and sealing devices, which enable the main frame structural compact, guide reliable, and easy to maintain. Slewing bearings are widely used for lifting machinery, excavating machinery, construction machinery, engineering crane, port machinery and ship machinery, electricity equipment, as well as other larger rotary devices, such as high-precision radar and missile launchers.