The main function of hub bearing is to bear the load and provide accurate guidance for the rotation of the hub. It bears both axial load and radial load. It is a very important part. The traditional automobile wheel bearing is composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of the bearing are carried out on the automobile production line. This structure makes it difficult to assemble in the automobile factory, high cost and poor reliability. Moreover, when the automobile is maintained at the maintenance point, the bearing needs to be cleaned, oiled and adjusted. Hub bearing unit is developed on the basis of standard angular contact ball bearing and tapered roller bearing. It integrates the two sets of bearings. It has the advantages of good assembly performance, omitting clearance adjustment, light weight, compact structure, large load capacity, pre loading grease for sealed bearings, omitting external hub sealing and free from maintenance. It has been widely used in cars and gradually expanded in trucks.