The slewing bearing is a large bearing that can withstand comprehensive loads and can withstand large axial and radial loads and overturning moments at the same time. The slewing bearing generally has mounting holes, internal or external gears, lubricating oil holes and sealing devices, so it can make the design of the host compact, easy to guide and easy to maintain. There are four slewing bearings, four-point contact ball bearings with external teeth and internal teeth, four rows of double-row angular contact ball bearings, cross cylindrical roller bearings, cross tapered roller bearings and three rows of cylindrical roller composite bearings Series, in which the four-point contact ball bearing has a higher static load capacity, the cross cylindrical roller has a higher dynamic load capacity, the pre-interference of the cross tapered roller bearing makes the bearing have greater support rigidity and rotation accuracy. The three-row cylindrical roller combined bearing leads to the height of the bearing due to the increase of the bearing capacity, and various forces are received by different raceways. Therefore, under the same force, the bearing diameter can be greatly reduced, so that the mainframe is more compact a high-capacity slewing bearing. Slewing bearings are widely used in large-scale slewing devices such as crane machinery, mining machinery, construction machinery, port machinery, marine machinery and equipment, high-precision radar machinery and missile launchers. At the same time, it can also design, develop and produce various special structure slewing bearing according to the specific requirements of users.