Abstract: Using Romax Designer engineering analysis software and ISO/TS 16281—2008 life calculation method, based on the classic rolling bearing theory, a large amount of calculations were conducted on the internal load distribution, contact stress, equivalent dynamic rolling element load of the ring raceway, and ISO/TS 16281—2008 life of a four contact point ball bearing for a certain motor shaft. The influence of the raceway groove curvature radius on the internal load distribution, contact stress, equivalent dynamic rolling element load on the ring raceway and ISO/TS 16281—2008 fatigue life of the bearing is emphasized. The research results indicate that when other conditions such as bearing model and manufacturing quality, load conditions, lubrication conditions, and reliability are determined, there exists a relatively optimal curvature radius (osculation) for the raceway groove. When the load conditions are different, the corresponding optimal curvature radius (osculation) of the raceway groove varies. Under the specific conditions studied, due to the different loads borne by the two bearings in the shaft system, the optimal raceway groove curvature radius (osculation) of the two bearings is different. The research results can provide a reference for the design scheme of motor shaft bearings.