The invention provides a 
thrust bearing for the screw of a ball-nut type steering gear. The 
thrust bearing comprises a screw. A thrust 
ball type thrust bearing is arranged on screw. The thrust 
ball type thrust bearing comprises a 
steel ball and a ring. The ring is composed of a left semi-ring and a right semi-ring. The cross section of the thrust 
ball type thrust bearing raceway is a four 
point contact type. The left semi-ring and the right semi-ring are both provided with a corresponding arc outer raceway. Two arc inner raceways are arranged on the screw. The 
radius of two inner raceways is the same as that of two outer raceways. The centers of four arc raceways are in a same circumference, but four arc raceways are non-concentric. The 
steel ball is arranged between the screw and the ring. Four contact points are formed between the 
steel ball and two outer raceways and two inner raceways, and thus a four 
point contact type thrust 
ball bearing is formed. In 
assembly, a 
punching-riveting anti-loosening structure is adopted between an adjusting nut and a valve body. For the bearing, a screw is used to replace a shaft 
washer, a holder is not needed any more, and the installation becomes convenient. The inner raceway and outer raceway are both composed of two arcs, a four 
point contact ball bearing is formed and is capable of bearing a large axial / radial force, the wear is reduced, and the service life is prolonged.