Abstract: 1n this article, the influence of the radius of fillet at the root of the gear tooth on its bending strength. Has been investigated by means of finite element method and experiment on bending fatigue. It has been proved that the service life of gear with increasing the radius of fillet is about three times of the original. It is an efficient way in the design of gear box as the allowable load is raised. The applicable- range of increasing the radius of fillet is discussed, and figures for seleting parameters of gear are given Project for the preshaving hob with increasing edge radius is also suggested.