Abstract: To clarify the process window in laser welding of asymmetric thin-shell structures with a thickness of 0.3 mm, a thermal-fluid-solid coupling model was developed based on a moving Gaussian rotating volumetric heat source implemented via FLUENT UDF. By comparing and analyzing the differences in temperature and stress field distributions with and without molten pool flow, the intrinsic mechanisms governing the driving forces inside the molten pool under asymmetric geometric constraints were revealed. The results show that for asymmetric ultra-thin structures, when molten pool flow is considered, the surface tension gradient driving force, i.e., the Marangoni effect, plays a dominant role, and the peak temperature and temperature gradient are lower than those without considering flow. Moreover, owing to differences in heat transfer under asymmetric constraints, the shift in temperature field distribution becomes more pronounced, and the transverse residual stress increases. Furthermore, comparison between experimental and numerical simulation results indicates that the weld cross-sectional dimensional error is smaller when molten pool flow is considered, which agrees better with actual conditions and verifies the importance of molten pool flow for accuracy evaluation. In addition, after parameter optimization, the welding speed is higher than that of existing high-power pulsed lasers.