Based on the rotary forging technique of spiral bevel gears, combining analysis of different trajectory forming curves, the forming laws of three kinds of trajectories including circular, spiral and rose trajectoies on tooth filling, axial load, metal flow, damage factor and temperature field were studied and analyzed by the finite element analysis software DEFROM-3D. The results show that the above five aspects have clear differences under the three different trajectories, and the tooth filling effect of rose trajectory is the best. However, the value and fluctuation of axial load under circular trajectory are the least. Furthermore, the material flows along axial, tangential and radial directions under spiral trajectory and rose trajectory, and the material flows along axial and tangential directions under circular trajectory. Thus, the evolution laws of damage factor and temperature field are also different because of different motion modes and change frequencies of swing head under three kinds of trajectories.