There is also a lack of differential designs. Advanced bearing design should be based on the bearing service environments so as to meet the requirements of the actual condition of bearings. Domestic individual and differential bearing design is still insufficient. In addition, heat treatment of bearing design is also an important factor that affects bearing life. Bearing includes four main pieces. There are outer ring, inner ring, rolling element and cage. Foreign bearing companies have special hardness requirements for the outer race and rolling elements of bearing products. But there is still a restriction on the hardness design of the bearings.