Hydraulic excavators generally use single-row four-point contact ball internal tooth slewing bearings. When the excavator is working, the slewing bearing bears complex loads such as axial force, radial force and overturning moment, and its reasonable maintenance is very important. The maintenance of the slewing bearing mainly includes the lubrication and cleaning of the raceway and the inner gear ring, the maintenance of the inner and outer oil seals, and the maintenance of the fastening bolts.