The different designs of rollers with varied convexity give different stress distribution and elastic deformation. It is directly related to the load capability and the life length of the roller bearing. With the Finite Element Method(FEM), by analyzing the stress distribution of roller busbar and raceway contact area in the design of different rollers with varied convexity of tapered roller bearing, the paper gets the best solution for the design of convexity of tapered rollers and the cause of roller bearings’ early destroy. The optimal result shows that the service life of this bearing has been improved by 93%. Hence, a more efficient method of improving the service life of rollers is got.