Abstract: In this paper, the gear model contains two gears and the inner gear is drived by a single parallel moving gear. Non-linear factors including gear backlash clearances, bearing clearances and gear meshing stiffness fluctuations are considered. Among them, the meshing stiffness fluctuations is resulted from multi-tooth contacting. based on these factors the differential equations of the motion are established. At different rotation speed the bifurcation characteristics of the system are investigated. The analysis results show that not only the collisions vibration characteristics of each motion pairs change with the rotation speed, but collisions vibration of each motion pairs are different from each other.