Abstract: The casting and forging composite forming process of the spiral bevel gear was analyzed. The microstructure of helical bevel gear castings and cast-forging composite moldings was observed and analyzed, and the effects of different forging process parameters on the microstructure of helical bevel gear casting and forging composite moldings were studied.The results show that the spiral bevel gear castings have no recrystallized structure, and fine and uniform recrystallized structure appears in the cast-forging composite moldings; with the increase of forging deformation, the grains of forming parts gradually become finer, with the decrease of the forging temperature and forging speed, the grains of the forming parts change from coarse to fine and then become slightly larger, and the new recrystallized nuclei all appear at the grain boundaries or high density dislocation. The optimal casting and forging process parameters of the spiral bevel gear are casting temperature of 1520 ℃, pouring time of 518 s, forging deformation amount of 40%, forging speed of 20 mm/s, forging temperature of 1050 ℃, environment temperature of 25 ℃, die preheating temperature of 200 ℃, and friction coefficient of 0.65.