Abstract: In order to weld high reflectivity aluminum alloy 5083H116 by laser-MIG hybrid welding process, the effects of the front and behind relative position of laser beam and arc on the formation of weld were analyzed.The laser beam incidence angel will seriously affect the weld formation both surface and inside corresponding to different formation mechanism.When the laser beam is in front of the arc in the welding direction, the weld surface is full uniform. While the arc is in front of the laser beam in the welding direction, the inclined trench will appear on the weld surface.With the help of EDX and micro hardness analysis, the Mg content shows a gradual increase from the weld upside surface to the underside surface, but the weld hardness is slight difference.The weld hardness of upside is less than that of underside for the laser beam in front of the arc in the welding direction;the weld hardness of upside is higher than that of underside for the arc in front of laser beam in the welding direction. Meanwhile, there is the black substance on the weld surface after welding, and it is confirmed as oxide of aluminum and magnesium by the EDX.