This paper presents a novel 3D numerical model of drilling CFRP to evaluate the degradation of mechanical properties in the hole surfaces. It can be used to determine the change of functional performance induced by accumulated damage. This function is realized through introducing damage evolution laws of the plies as well as the interfaces into the model. The damage level within plies leads to the degradation of stiffness of the hole surfaces. The simulation results are validated against cutting forces, torques and delamination, then the degradation of stiffness matrix is evaluated through prediction. This model is the first to merge different progressive damage evolution laws in drilling CFRP, which is beneficial for understanding the damage mechanisms in hole surfaces, and can be used to optimize CFRP drilling processes by reducing damage, delamination, and subsequent degradation of the workpiece stiffness.