Abstract: Thermo-mechanical parameters varied with temperature were used to compare qualitatively the influence of the yield strength, heat conductivity, specific heat capacity, Young's modulus, coefficient of thermal expansion, density and Poisson ratio on the peak welding residual stress.The result shows that the change of yield strength and heat conductivity is wide, which have greater effects on the peak welding residual stress.Whereas, specific heat capacity, Young's modulus, coefficient of thermal expansion and density show little influence on it.The change of Poisson ratio is close to that of thermal expansion and density, however, its influence is little.The simulation results of welding longitudinal residual stress were verified with cutting pieces stress relieving method for the flat plates with such material properties as 2A12-T4 aluminum alloy.The results have good agreement with tested results, which prove the validity of the simulation results.