In the traditional laser welding of thin-walled aluminum alloy T-type welds, there are problems such as limited welding station, difficult control of process stability, and easy generation of defects. This study proposes a novel oscillating laser–arc hybrid welding method for aluminum alloy double-seam T-joints to solve the above problems, and welding process test and fluid dynamics analysis of weld pool were carried out. The results show that the oscillating laserarc hybrid welding can effectively inhibit the defects such as porosity, depression, and undercut in the three-sided welding process of single-pass laser welding. In laser–arc hybrid welding process, the transition of the droplet to the molten pool significantly enhances the flow rate, accelerates the heat and mass transfer from the center of the molten pool to the sides, which maintains the stability of keyhole while improving the melt flow characteristics.