In this paper, thermo-mechanical behavior of the welding process was analyzed to determine the effect of edge preparation on the residual stress magnitude and distribution in dissimilar joints. By using a verified finite element model, an efficient user subroutine was developed to consider the effects of phase transformation. In order to verify the model, experimental data for similar and dissimilar joints, obtained by deep hole drilling method, were utilized. Good agreement was observed between the finite element and experimental data. The results indicated that the developed computational method is an effective tool to predict the residual stress of dissimilar weld joints. The present finite element model was developed in a butt-welded pipe to consider the effect of pipe wall-thickness, groove shape and root opening distance. It was observed that the pipe wall-thickness has important influences on the distribution and magnitude of residual stress. Moreover, By increasing the pipe thickness in the dissimilar butt-welded pipes, tensile axial residual stresses on the inner surface of the dissimilar joint decreased on the stainless steel side, but only a small variation was observed on the carbon steel side. compressive axial residual stresses on the inner surface and the tensile axial residual stresses on the outer surface increased by increasing the pipe wall thickness especially on the carbon steel side. Increasing of the weld groove shape and root opening distance lead to higher compressive axial stresses on the inner surface and higher tensile axial stresses on the outer surface, only on the carbon steel side.