Abstract: A three-degree-of-freedom vibro-impact system is considered in this paper. Based on the solutions of differential equations between impacts, impact conditions and match conditions of periodic motion, the six-dimensional Poincaré maps of periodic motion are established. The two-parameter unfoldings of local dynamical behavior in resonance are investigated. By numerical simulation, as two controlling parameters varying on the two-parameter plane, the topology regions of parameter plane are divided. An invariant torus via Hopf bifurcation and period motions via subharmonic bifurcation are analyzed, which are characterized by “four-square” and “four-leaf ” different lodge orbits and exist near the critical point, and the route from order 4 subharmonic bifurcation to chaos is further analyzed.