Abstract: A vibro-impact forming machine with double masses and a harmonic excitation is studied based on the Poincaré mapping in this paper. Stability and local bifurcations of single-impact motion of period n are analyzed using bifurcation theory of mapping. Global bifurcation of single-impact motion of period n and transition to chaos are investigated by numerical simulations. The influences of system parameters on single impact period-one motion, single impact subharmonic motion and chaos are discussed. It is found that the stability and global bifurcations of the vibro-impact forming machine have important significance in optimization design and noise suppression of the machine.