Abstract: The ultrasonic-assisted extrusion process of automotive starter gears was investigated based on Deform-3D software in this study. Conventional extrusion（without ultrasonic vibration assistance） was used as a control experiment. A finite element model was established, and the variations in load, stress field, strain field. and forming temperature during the extrusion process were analyzed. The results of the control experiment showed that, under the influence of ultrasonic-assisted vibration, the peak load was reduced by 4.7%, and the average load was reduced by 7.5%. The maximum equivalent stress was reduced by 9.13%, and the average equivalent stress was reduced by 9.8%. The working stress and load on the tools and dies were reduced, which was considered to have potential significance for extending their service life. The equivalent strain and forming temperature were increased by 9.3%and 5%, respectively. The increase in billet temperature was found to be beneficial for improving plasticity and reducing internal stress. The increase in equivalent strain indicated that metal deformation was more thorough, and the enhanced metal flow was conducive to filling the mold cavity.