Abstract: To analyze the deformation of large-scale thin-walled spherical shells during pre-deform TIG welding process, a sub-structure analysis method is proposed based on non-linear numerical calculation procedure. The whole structure is divided into two parts, which are flange-skin substructure and the other part of the shell. First, the pre-deformation of the substructure is analyzed, based on which its thermo-stress field could be obtained by means of thermo-plastic analysis. Afterwards, the substructure is assembled with the other shell part and the constraints are removed, and the residual stress and strain fields of the whole structures could be obtained. The results reveal that, when the pre-stress along the inner edge of the skin reaches its yield stress, the residual deformation would be reduced by 65%.