Abstract: By using ANSYS, the 3D temperature field of laser welding for aluminum alloy of different thickness were simulated. In order to improve solution accuracy and efficiency, transition mesh and Gauss function heat source model were used, and APDL in ANSYS was used to compile program to realize the load of moving heat source.The effects of temperature-dependence material parameters and potential heat, boundary conditions, plasma, convection in molten pool and characteristics of different thickness were considered in the model.Using high-temperature thermocouple, the temperature was measured.It is shown that the simulation results are in accordance with the experimental results.