Abstract: The wire melting rate in AC Pulse MIG welding is mainly affected by the current and EN ratio aluminum alloy, the wire melting rate increases dramatically as the welding current increases at a constant EN ratio;at a constant welding current, the wire melting rate increases gradually as the EN ratio increases.On the basis of differences in equivalent cathode/anode drops and the welding arc characters in EN/EP polarity, the welding wire gets more energy as the EN ratio increases, so the wire melting rate is larger than DC MIG welding.At a constant wire feed speed and welding speed, the penetration depth and bead width decrease while the reinforcement becomes high as the EN ratio increases.Accordingly, AC Pulse MIG welding technology can solve the burn through problem in welding thin sheet joints and can greatly improve the gap bridging ability in lap joints.What is more, this technology can also improve the welding speed and welding bead quality for thin sheet joints.