Complex profile broaches are widely used in the manufacture of complex parts of aero-engines, but their cutting forces in the broaching process are difficult to predict and control. A new numerical model for broaching force with complex profile tools is presented, which considers the area and arc length of curved shear zone projection. The area and arc length were calculated by the curve function of the projection plane, which is firstly predicted by FEM simulation. Compared with the conventional force model, the accuracy of the modified model has been moderately improved. Ultimately, the modified main broaching force (Y-direction) model and the modified normal force (Z-direction) model show a significant improvement in accuracy by 4.8% and 9.7%, respectively. It suggests that the projection area of curved shear zone A1 and the projection arc length of curved shear zone l1 have a big impact on the broaching process. Moreover, the modified model proposed in this paper can provide guidance for the design of complex profile tools and facilitate the efficient and high-precision machining of complex parts.