Abstract: According to the typical connection form of the roof components of a certain electric multiple unit, three typical fusion-active gas shielded arc welding joints including butt joint, lap joint and fillet joint were prepared. Finite element models were established based on the thermal elastoplastic method and the temperature load method respectively to simulated and verify the welding deformation of the joints. The buckling deformation of the roof under a load of 300 kN was simulated and calculated considering and not considering the welding residual deformation, and the stability of the roof was analyzed. The results show that relative errors between the maximum angular deformation of the three joints simulated by the thermo-plasticity method and the temperature load method and the experimental results were all less than 5%. The accuracy of the welding deformation predicted by the two models was both relatively high. Compared with the thermal elastoplastic method, the temperature load method reduced the number of meshes and calculation time by more than 90%, so the temperature load method was selected for the stability analysis of the roof. According to the sub-model calculation, the first-order buckling factor of the roof without considering the welding deformation was 2.494, which was greater than the safety factor (1.5), indicating that the roof did not lose stability under a load of 300 kN without welding deformation. When considering the welding deformation, the first-order buckling factor was 1.131, indicating that the roof lost stability under a load of 300 kN when there was welding deformation.