Abstract: In order to explore the application of 3003 aluminum alloy in power battery casing and other fields, laser swing method was used to carry out welding process experiments on 1. 5 mm thick 3003 aluminum alloy sheet, microstructure and mechanical properties of the welded joint were analyzed. The results showed that under surface focusing conditions, a well-formed welded joint could be obtained at 40 mm/s welding speed, 1 350 W laser power, 5 000 Hz pulse frequency, 100 Hz swing frequency and 0. 3 mm swing diameter. There existed a fine-grain zone at the fusion line of the welded joint and the center of the weld. The transition area from the fusion line to the center of the weld was composed of columnar crystals and the overall microstructure of the joint was refined. The hardness of each zone of the welded joint was higher than that of the base material, the tensile strength was about 91% of that of the base material, and the elongation after fracture was about 65% of that of the base material. The fracture form of the joint was a mixed fracture of toughness and quasi-cleavage.