The inner wall of static bearing of an advanced high temperature liquid metal pump needs to be surfacing with large area of stellite alloy. Due to the high hardness and poor toughness of the stellite alloy,the preheating temperature is high,the cooling speed of molten pool is slow,and the continuous welding time is long. Therefore,the final surfacing layer is prone to crack,incomplete fusion,porosity and other problems. According to the existing pores in the surfacing layer,the possible causes were investigated one by one,and the main reason is finally determined to be moisture. According to the powder drying test and surfacing test before and after drying,the welding defects were reappeared. It is stipulated that the welding powder must be dried at 250 ℃×2 h before surfacing to avoid the porosities.