Abstract: The paper introduces a method of grinding the inner runaway of the rings with CBN grinding wheel replacing Al2O3grinding wheel,determines the desired properties of CBN grinding wheel,and designs a CBN grinding wheel and a set of diamond wheel dresser for it.It makes an in-depth study of the CBN wheel′s dressing parameters,such as the velocity rate of dressing,clockwise or anticlockwise dressing etc.It indicates through actual use that both the grinding precision and surface quality of the inner runaway of the ring have been improved,the roughness is reduced fromRa0.4μm toRa0.2μm,the dimension has the same accuracy,and no phenomenon of grinding burn is found.Each pair of CBN grinding wheel can grind more than 3 000 pieces of ring,extending the life span of the grinding wheel more than 50 times,while the productivity has been increased by 3 times.