In this paper, laser-MIG hybrid heat source is used to conduct welding experiments on 6.9 mm thick plates of 5A06 aluminum alloy. The paper analyzes the weld macroscopic morphology with different welding parameters. The change trend of weld microstructure with temperature gradient is studied, and the reason for the change in microhardness is explained. The research results illustrated that the four welding parameters adopted in this experiment achieve good weld formation, while defects such as lack of penetration, undercut do not exist in the welds. The depth to width ratio of four welding parameters are all above 1.5, Case 4 can achieve 2.04. In addition, with the decrease of the welding line energy, the cooling speed of the weld joint is accelerated and the strengthening phases such as Mg2Al3 in the weld is increased. It resultes in the increase of microhardness of the weld along the direction perpendicular to the weld centerline.