Abstract: Because of concentrated welded seams and complicated welding stresses, the integral sizes of tank are often out of control during tank welding, which yields a poor installation quality. From respect of welding process in tank shell and tank bottom and welding method, the paper analyzes the welding deformation and other factors, such as welding method as well as steel plate quality that influence welding quality, and put forward the effective measures to be taken to control the welding deformation during welding.