Abstract: The GIS aluminum alloy shell is mainly formed by welding,which has certain requirements on assembly precision. If there exists more serious welding deformation and residual stress,which will affect the quality of the product. In order to study the influence of the welding process on the quality of the product,being taken the flange and cylinder as the object,the finite element software SYSWELD was used to simulate the temperature field and stress field during welding to obtain the thermal cycle curve,deformation and the distribution of residual stress. The results show that the first weld is heated by many times,and the peak temperature is close to the annealing temperature. The flange has the whole inclineand uneven deformation of the surface. The wavy deformation appears in cylinder. The residual stress mainly distributes in the root of the first weld and in the whole second weld. The simulation results can provide reference for controlling welding process of GIS aluminum alloy shell.