The processes, testing and application technology research were carried out for the welding synchronous laser cleaning of aluminum alloy for rail transit vehicle carbodies. The process window of laser cleaning for oxide film of aluminum alloy was obtained through the study of process. The prediction model of laser cleaning parameters before matching different welding speeds was established. And the effect of laser cleaning on the superficial oxide film of aluminum alloy was analyzed. According to the actual working conditions, an integrated laser cleaning and arc welding synchronous device was designed. And the pre-welding synchronous laser cleaning process verification was carried out. High-quality and high-efficiency removal of oxide film before welding was achieved. By analyzing the mechanical properties of welded joints, detecting weld defects and observing the microstructure of the cross-section of the welded joint, the quality of welding synchronous laser cleaning welds was evaluated. The research shows that with 200 W pulsed laser, the cleaning speed is adjustable from 0.5 to 1.1 m/min. Welding synchronous laser cleaning of oxide film with a line width of 45 mm can be effectively achieved. After laser cleaning, the primary oxide film is completely removed and the effect of regenerative oxide film can be avoided. The shear strength and strain of the welded joint after laser cleaning before welding increased by 26.4% and 9.98% compared with the untreated joint. The shear strength and strain of welded joints after laser cleaning increased by 3.53% and 1.43% respectively compared to those after manual grinding. And the central microstructure of the weld was mainly composed of α matrix and β (Mg₂Al₃) phase. The performance of the welding met the requirements of rail transit vehicle carbody manufacturing. Laser cleaning with welding can effectively replace manual grinding technology.