Abstract. This study used finite element software SYSWELD to analyze residual stresses in butt-weld between underframe and side wall of high-speed train car body. Based on the thermal-elastic-plastic theory, double ellipsoid heat source model is adopted to simulate the residual stresses under different heat input in the welded joints between underframe and side wall. The residual stresses at the surface of weld specimen were measured experimentally by using the hole-drilling method. The results of the ﬁnite element analysis were compared with experimentally measured data to evaluate the accuracy of the ﬁnite element modeling. Based on this study, a modelling procedure with reasonable accuracy was developed. The developed ﬁnite element modelling was used to study the effects of welding heat input on magnitude and distribution of welding residual stresses in butt-weld of high-speed train car body made of A6N01-T5. The results show the maximum residual stress exists in the welded seam and the adjacent-weld zone, and the residual stress value decreases gradually while the zone is farther from the weld center .Besides, With the increase of the welding heat input, the residual stress value increases gradually.