Abstract: The welding performance and welding process of top nozzle in native is intruduced.Base on the analysis of a large number of the weldability test on the special material,such as deposited performance and uniformity test,welding base metal penetration performance test,and nozzle entity welding,the welding parameter satisfying the welding technology requirement and the welding technology qualification is obtained.The form of butt welded joint is without groove.Firstly the assembled nozzle tack welding is carried out manually,and then the weld is conducted without filler metal by robot.Repair welding of nozzle can be conducted by filler metal if necessary.The method of variable speed welding can be adopted to increase the welding speed in the plate spring stage and the ending stage.The results from the process appraisal using the new welding procedure satisfy the requirements of the technical conditions.