Slewing bearing is a kind of special structure large bearing, including rotating, transmission, fixed and other functions. And it can carry high axial load, radial load, and overturning moment load at the same time. Under normal circumstances, the slewing bearing itself both with teeth, mounting holes, lubricant holes and sealing devices to meet the requirement of variety of working conditions. On the other hand, slewing bearing has a characteristic of compact structure, easy to guide rotating, convenient installation and easy to be maintained, widely used in lifting and transport machinery, mining machines, construction machinery, port machinery, wind power generation, medical equipments, radar, missile launchers and other large rotary devices.