Abstract: In order to better understand the ultrasound-MIG welding process,the arc behavior during ultrasonic-MIG welding of aluminum alloy was investigated in this paper. The response of ultrasound-arc was explored at different wire feeding speeds or welding voltages. The results show that the compression effects of ultrasound-arc varied with different welding parameters. With the increase of wire feeding speed,the compression gradually became weaker. According to the results,the analysis of ultrasound-arc self-adjusting was carried out. Compared with the traditional MIG welding,the electric field strength and temperature in ultrasonic arc were greatly enhanced and led to stronger welding stability.