Numerical simulation based on finite element modeling is used widely for the prediction of welding residual stress and distortion. Considering this method, the accuracy of the ultimate result of the residual stress and distortion field is depended greatly on the accuracy of the welding temperature field. The APDL languages of ANSYS procedure was used in this study. In order to model the addition of the filler to the weld, element birth and death technology was selected. It well performed to simulate the moving of the heat source and the process of transient thermal convection. The results show that the change process and the distribution of the welding temperature field agree well with the weld reality.