In the spiral bevel gear of cold finishing process, optimization of hot forging die tooth to improve the flow characteristics of the cold finishing process of tooth filled metal, the top discontent is solved, and the phenomenon of gear transmission noise has a significant effect. This selection of agricultural machinery based on the gear transmission gearbox, big power, high strength, working environment for the low speed and high load characteristics, accurate modeling of gear model, and Tooth Contact Analysis (TCA), the cavity model was obtained by introducing tooth surface point way. The control variable method and numerical simulation were combined with the change of cutter diameter repairing tooth surface of the drum. The finite element software DEFORM-3D was used to simulate the forming process, and the velocity vector of the two kinds of tooth surfaces were observed and compared to explain the rationality of improving metal flow direction by modified method. Through the open model test, further confirmed that the modified method has a significant advantage in improving the filling of the top of the spiral bevel gear and solving the problems such as folding and crack