A mechanical model of twodegreeoffreedom system with clearance was established,whose periodic motion and disturbed motion were studied. The Poincaré mapping of the system was established by selecting the appropriate Poincaré section and the periodic conditions of vibroimpact. The existence of Hopf circle was proved by Poincaré mapping numerically. The route to chaos through Hopf bifurcation and perioddoubling bifurcation of this system was revealed. Finally, the impact of the system parameters on the dynamical behaviors of this system was analyzed,and the theoretical criterion for the optimal design of dynamical systems was found.