Abstract: The static diaphragm is an important part in steam turbine.And welding deformation in the production of diaphragm is a main problem for the production of steam turbine.In order to minimize the welding deformation of diaphragm,the records of welding deformation are obtained through directly measuring size of the diaphragm with coroneted blades before and after welding.The welding deformation of the diaphragm in radial and circumferential direction is analyzed with the recorded data after the main welds of the diaphragm with coroneted blades are welded and the diaphragm annealed respectively.The design measures for reducing the welding distortion are applied primely.