Abstract: The MIG welding test of 20 mm thick 6061 aluminum alloy plate was carried out by using ER5356 welding wire with diameter of 1.2 mm. The joint was detected by RT, UT and PT, and the microstructure was observed, the tensile, hardness and bending tests were carried out. The results show that the RT, UT, PT results of the 6061 aluminum alloy joint are qualified. There are no defects such as porosity, slag inclusion, crack and lack of fusion in the joint. The weld surface is beautiful, and the welding deformation is small. The tensile strength of 6061 aluminum alloy joint reaches 231 MPa, and there is no visible crack on the inner and outer surface after 180° bending. The hardness of the weld zone of the joint is the lowest. There is a softening zone in the heat affected zone. The hardness of the softening zone is 79.8 HV, which is still higher than that of the weld. The microstructure of the weld is composed of α- (Al) matrix and β-Mg₂Si. The microstructure of the weld zone is composed of coarse equiaxed grains. Along the heat dissipation direction of the weld, the equiaxed grains gradually change into columnar grains, and the columnar grains transits to dendrite along the direction perpendicular to the fusion line.