Milling force is an important parameter during machining, which is directly related to the tool deformation, the tool life, the quality of the part surface, cutting heat, etc. In actual production, the cutting force on inside corner is more complex than the linear. For lack of the accurate cutting force information, there is liable to cause over-cut and owes-cut, rough surface, cutter breaking phenomenon. According to the structural characteristics of the corner, the cutting force model is established, which cutting force is further subdivided and the overall prediction accuracy is improved. Effects of different helix angle and forward amount each gear on cutting force. A good agreement is shown between the model simulation and the results of the experimental ones. The research provides a theoretical basis of predicting the cutting force on inside corner, and it is also helpful for further and practice.