The finite element simulation of friction and wear experiment on TiN film/carbon steel substrate system shows that several stress concentrations at edge of grinding- trace, tensile stress inside and outside grindingtrace, shear stress at film/substrate interface all affect tribological behavior of the system. The results calculated by FEM have been confirmed by pin/disc test. According to the analysis of crack initiation and propagation in film as well as damage and breakage of system, the process of friction and wear can be divided into several stages, such as wear - in, steady wear, film unsteady wear, and system failure. The failure mechanism of hard film/soft substrate system in friction and wear experiment under small loading has been suggested. The stress concentrations and tensile stress have important function on crack initiation and propagation, which can cause the brittle breakage in film. The stress concentrations at edge of grinding - trace due to deformation play most important role on early damage which results in wear failure of film/substrate system.