Abstract: The backing welding of 5083 aluminum alloy plate was carried out by hybrid welding laser and melt inert-gas arc (MIG) welding to simulate the one-sided welding with back formation of aluminum alloy tank. The influence of laser beam swing mode (no swing, straight swing, circular swing, square swing),laser power (2.5-4.0 kW), combined gap (0,1 mm), and misalignment (0,1 mm) on weld seam formation quality was studied, and the mechanical properties of welded joint under the optimal process were analyzed. The results show that at 3.0 kW laser power, when the laser beam did not swing, the back of the weld seam was discontinuous and accompanied by pits; when the laser beam swing mode was the straight mode, there were a lot of pores in the weld seam. In the circular laser beam swing mode, no continuous full penetration weld seam was formed on the back of the weld seam at the laser power of 2.5 kW, and the weld seam appeared serious collapse at the laser power of 4.0 kW. The laser power of 3.0-3.5 kW and the circular or square laser beam swing mode could realize the free forming of the back side of one-side welding, and the weld seam was well formed, showing a strong adaptability under different combined gaps and misalignments. Under the optimized process of 3.0 kW laser power and circular laser beam swing mode, the tensile strength of the welded joint could reach 90% that of the base metal, and there were no cracks and other opening defects in the joint after positive bending and back bending, which met the requirements of engineering application.