Abstract: A new technology of three-wire MAG high speed welding is researched to replace two-wirewelding technology which is usually used to weld fillet in shipyard and the welding speed is under 1.0 m/min.Three wires, namely, leading wire, middle wire and trailing wire, are arranged in tandem.Each wire is equipped with separate wire feeder system, power supply and gas shield device, and welding process parameters can be adjusted individually to meet the various requirements of welding.The results show that the polarity combination of leading wire (DCEP)/middle wire (DCEN)/trailing wire (DCEP)or that of leading wire (DCEN)/middle wire (DCEP)/trailing wire (DCEN)can obtain stable welding process, good weld appearance, symmetrical weld seam, non-porous weld to meet the requirements of the shipbuilding industry;the maximum welding speed can be up to 1.8 m/min and the length of fillet weld leg can be to 5-8 mm by selecting a suitable welding current and welding speed.This new welding technology can be widely used for highspeed fillet welding industry.