Abstract: The simulation of welding process of the large stringer steel foundation was established by thermal elastic plastic FEM. By adopting double ellipsoid heat source method, the temperature field and stress field were calculated, therefore the residual stress and the deformation of the foundation structure were acquired. Bedsides, the influences of sequence of four weldings and the three foundation constraint ways on the welding deformation were analyzed.Resultsshowed that under the double restraints of mound layer and tack welding, the deformation was the slightest, and that by optimizing the welding sequence and fixture arrangement, the welding deformation could be reduced effectively.