Thrust ball bearings in made up by following three parts, seat ring, axes ring, and steel balls together with retainer. The part assort with axes is called axes rings, while part assort with crust is called seat rings. According to the force situation, thrust ball bearings can be divided into one-way thrust ball bearings and two-way thrust ball bearings. One-way thrust ball bearings can endure unilateralism axial load, while two-way thrust ball bearings can stand bidirectional axial load. The rings and axes assort with each other in two-way thrust ball bearings. The installed surface of seat rings, which is in shape of sphere, have the function of self –aligning, what’s more, it can also minimize the effect of error during installing.