The cutting edge radius is an important factor affecting the machining quality of carbon fiber reinforced polymers (CFRP). In order to study the influence of cutting edge radius on cutting mechanism in CFRP milling process, a two-dimensional micro simulation model was established. The accuracy of the cutting model was verified by comparing the cutting force obtained from the experiment with the simulation value. Using this model, the changing rules of cutting force, cutting mechanism and subsurface damage under different cutting edge radius were analyzed. The results show that the influence of fiber orientation on cutting force is greater than that of cutting edge radius. When the fiber orientation is 45°, the cutting force increases with the increase of edge radius, but fluctuates less at the other fiber direction angles with the change of edge radius. With the increase of the cutting edge radius, the cutting process of CFRP changes from shear failure to bending failure. Small cutting edge radius causes small subsurface damage depth and small cutting force. However, it will lead to excessive stress at the edge, and there is a risk of tipping.