Main feed water control valve is a very important nuclear safety control valve in the nuclear power plant. In order to enhance the wear resistance of the sealing surface,it is necessary to perform build-up welding on the contact sealing surfaces of the valve with Stellite alloy. The advantages of plasma build-up welding are easy to realize automation,high production efficiency,low labor intensity and low weld dilution rate. It can greatly improve the surfacing production efficiency and welding quality. In this article,the reasons of cracking in Stallite build-up welding of sleeve of main feed water control valve are analyzed,and welding quality control measures are proposed. It can provide useful reference for domestic valve manufacturers to surfacing cemented carbide.