Abstract: The thermal-fluid coupling model of 2219 aluminum alloy T-type structure with dual laser-beam bilateral synchronous welding (DLBSW) was established to explore the relationship between the driving force of molten pool and flow field during DLBSW process. The driving effects of surface tension, recoil pressure, gravity and thermal buoyancy on molten pool flow field were analyzed, and the mechanism of molten pool flow field under combined influence of driving forces was indicated. The results show that: the flow fluid on the surface of molten pool is mainly driven by surface tension; the circulation formed at the left and back of the bottom of the molten pool are mainly co-driven by surface, gravity and thermal buoyancy; the bottom of molten pool below keyhole flows along the edge of molten pool under co-driven of gravity and thermal buoyancy.