In this study, a procedure for the more accurate numerical simulation of weld distortion and residual stress,which was developed on the basis of heat source modeling by considering the physics of the welding arc, is applied to the AC TIG arc welding of aluminum alloy. The Gaussian distribution of heat source in the TIG arc welding,which is a function of the weld heat input per unit time and Gaussian radius, was determined depending on the welding heat input conditions. Using the developed heat source model, the numerical simulation of weld distortion and residual stress was performed to compare the measurement results under the same welding conditions. As the results, the simulated weld penetration, distortion and residual stress were in good agreement with those measured. In addition, a more quantitative characterization of the effect of weld heat input conditions on weld penetration and distortion has become possible through the developed numerical simulation technique. Thus, the verication and validation of the developed numerical simulation model has been achieved through a comparison with the experimental results with a focus on the e−ect of weld heat input conditions.