Abstract: Through temperature measurement experiment and temperature field simulation, the problem of 2024-T4 alloy friction stir lap welding（FSLW） reduced joint strength arising from elevated peak temperature at the end is found. To address the problem, it is proposed to reduce the rotational speed of the stir tool at the end welding, thereby reducing the peak temperature at the end welding and making its performance consistent with that of the steady-state welding. The regulated rotational speed of the stir tool at the end welding is jointly obtained from combining temperature field simulation and the temperature measurement tests. Through the analysis of internal formation characteristics of the steady-state and end welding before and after the adjustment, it is known that the rotational speed adjustment scheme for the final section of the weld during the welding process, derived from temperature field simulation, reduces the temperature peak fluctuations between the steady-state region and the final section less than 5%. Consequently, similar interfacial morphology and tensile-shear strength are achieved between the final section and the steady-state region of the weld. The study takes into account the impact of heat accumulation during the process on joint performance, which can provide valuable insights for future research on the influence of temperature on joint properties.