Abstract: A dynamic model for vibro-impact system with clearance has been established based on generalized Hertz contact theory, which is numerically solved by 4-5 order Runge-Kutta method. Non-linear vibration characteristics of the model is studied by analyzing the bifurcation diagrams, the phase diagram, the Poincaré maps and the power spectrum chart respectively obtained at different frequency ratios, exci-ting force amplitudes and clearances. Results show that period, period doubling and chaotic motion occur in the vibro-impact system with the variation of frequency ratio, amplitude of exciting force and size of clearance, among which the frequency ratio and amplitude of exciting force play an important role in influencing the non-linear vibration characteristics, when broad chaotic bands appear; the size of clearance effects little on the system response, however, within the small variation range of clearance, the vibration characteristics change greatly.