Aiming at the welding arc stability of aluminum alloy welded by pulse MIG,this paper used the rapid prototype pulse MIG welding power source development platform to control arc length by adjusting pulse duty ratio and pulse frequency. Taking the average arc voltage changes as the feedback signal,the control module of pulse MIG welding power source development platform was designed. The real-time arc control experiment of aluminum alloy was carried out by pulse MIG. The welding tests proved that the control system had good dynamic performance,anti-jamming performance and steady state accuracy. Also,the control system realized the fast and effective control of arc length,obtaining a stable welding process and forming a good weld appearance.