Abstract: By finite element code ANSYS, the 3D stressstrain fields of aluminum alloy joints in different thickness made by laser welding were simulated.In order to improve the accuracy and efficiency, transition mesh was used.The effects of temperature-dependent material parameters were considered in the model.The bilinear kinematical hardening (BKIN)was established.Proper restrictions of displacement were applied for simulating effect of clamps.The result of simulation indicates that, the stress-strain field in the thin plate is larger than the thick one.Using hole-drilling technique, the residual stress was measured.It is shown that the simulation results are in accordance with the experimental results.