Abstract. Abrasive flow machining (AFM) is an effective method that uses the flow of a pressurized abrasive media for removing workpiece material. It is used to deburring, polishing or radiusing, etc. In this paper, the effect that AFM process on the surface of the helical gear is investigated. Then, the distribution of the velocities, shear rates and shear forces of the abrasive flow on the helical gear surface is obtained by CFD module of the COMSOL Multiphysics software. The simulation results show that the abrasive grains near the addendum, tooth surface and tooth root can be subjected to corresponding shear stress. Experimental results indicated that the surface roughness Ra of the left tooth surface, right tooth surface and addendum before processing 1.429um, 1.108um and 2.732um dropped after processing 0.228um, 0.216um and 1.754um. All burrs at the intersection between tooth surface and end surface has been cleared, the surface quality of the helical gear has been improved. Therefore, AFM method can improve the surface quality of the helical gear effectively.