Abstract: When using MIG Welding with micro-addition of nitrogen for the aluminum alloy of 5086, it was found that the welding penetration related with welding productivity was increased without a loss of soundness and the mechanical properties compared to the weld using pure argon.This phenomena can be ascribed to:1) the formation of aluminum nitride layer resulted in the reduction of the spot of cathode and the increase of arc energy density, 2) the aluminum nitride could suppress the cathode energy loss because of the metal vaporization.