The main function of the wheel hub bearing is to bear the load and provide precise guidance for the rotation of the wheel hub. It bears both axial load and radial load, and is a very important component. Traditional automobile wheel bearings are composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of the bearings are all carried out on the automobile production line. This structure makes it difficult to assemble in the automobile factory, high cost, poor reliability, and the bearings need to be cleaned, oiled and adjusted when the car is maintained at the repair point. The wheel hub bearing unit is developed on the basis of standard angular contact ball bearings and tapered roller bearings. It integrates two sets of bearings and has the advantages of good assembly performance, omitting clearance adjustment, light weight, compact structure, large load capacity, grease can be pre-loaded for sealed bearings, omitting external wheel hub seals and maintenance-free. It has been widely used in cars and there is also a trend of gradually expanding its application in trucks.