In the existing high-strength steel gear processing and manufacturing process, generally after grinding finishing, the gear has a good surface roughness. In order to obtain good fatigue characteristics of the gear, especially in terms of bending fatigue strength, often in the grinding process after shot peening. However, after shot peening, the gear surface roughness value increases, the surface integrity decreases, which is not conducive to the generation of oil film in the meshing process of high-strength steel gear, reducing the lubrication performance and fatigue life. Therefore, after shot peening, the gear needs to be hobnail grinding and finishing. However, at present, the processing mechanism of hobbing finishing is unclear, and the influence of processing parameters on the surface roughness is not clear. In this paper, starting from the mechanism of hobbing finishing, we establish a simulation and analysis model based on Engineering Discrete Element Method (EDEM) for hobbing finishing of gears, and analyze the simulation results to get the gear speed, drum speed and other influences on the gear tooth surface force and surface roughness, and to realize the reduction of surface roughness on the tooth surface of gears made of high-strength steel. The surface roughness value of the gear teeth of high-strength steel can be reduced.