Abstract: The microstructure, hardness and residual stress of M50 steel bearing rings, carburized M50NiL steel bearing rings and M50NiL steel bearing rings after compound chemical heat treatment of carburization and nitridation were tested and analyzed. The hardness tests, stress tests and life durability tests were carried out on M50 steel bearing rings and carburized M50NiL steel bearing rings. The results show that:after compound chemical heat treatment, the hardness of surface and core of M50NiL steel bearing rings was improved compared with that of carburized M50NiL steel bearing rings, and the surface stress especially the subsurface stress was greatly improved, as a result, the abrasion resistance and fatigue properties were also greatly improved; the fatigue resistance and service life of carburized M50NiL steel bearing rings were enhanced by 3 to 5 times compared with those of M50 steel bearing rings.