steel lining of nuclear power station implementing modular design,need dividing the circumference of cylinder of steel lining into a number of plate modules,and each module of cylinder is assembled and welded integrally after individually welding,but the radial welding displacement of plate edge of cylinder is not more than 2 mm.Therefore,by using the software of ABAQUS,the welding deformation of plate of cylinder are simulated with pre-stress,and design pre-stress tooling structure by oneself,test prestress of plate of cylinder and the radial deformation after welding.The results indicate that the welding process that firstly welding the axial angle steel,then exerting the pre-stress,lastly welding the circumferential angle steel,can obviously reduce the radial deformation of plate edge of cylinder,with the increment of pre-stress welding deformation is decreasing exponentially.When the top lift of oil cylinder reaches 18 MPa,the radial deformation of palate edge can control within 2.0 mm.