Abstract: The welding process of 5A06 aluminum alloy was tested by laser-MIG hybrid welding. Effects of laser power,defocusing amount,welding speed and optical wire spacing on weld formation were analyzed. The results showed that the welding window was narrow,the welding process was unstable,and the forming defects such as hump,depression and undercut were easy to appear in the weld. The laser power,defocusing amount and welding speed had great influence on the weld penetration. When the laser power increased from 10 kW to 30 kW,the weld penetration increased by 18 mm to 29 mm. The influence of laser-arc spacing on penetration and width of weld was small. By adjusting welding parameters,the weld formation of aluminum alloy could be improved obviously. Under the appropriate welding parameters,the weld with stable surface formation could be obtained at the same time of reaching the maximum penetration.