In order to improve the dynamic characteristics of face-gear drive system, the modified method for face-gear drive system is studied, and the equations of the cylindrical gear, altter gear and face-gear are obtained. The dynamic model is established by the concentrated parameter method, which includes modified backlash, time-varying meshing stiffness, profile modifying parameter, general transmission error, brace stiffness, support damping, etc. The Runge-Kutta numerical integral method is used to calculate the dynamic equation. The results show that changing the modified parameter will change the dynamics characteristics of the face-gear drive system, and three kinds of steady state responses, i.e. harmonic, sub-harmonic and chaotic responses are shown.