The hardfacing procedure of the latch with cobalt-base alloys about the third-generation nuclear power control rod drive mechanism is mainly studied from the aspects of the material weldability,oxyacetylene welding method,welding flame type,welding nozzle size and preheat. And the chemical composition,metallographic microstructure and surface hardness of the hardfacing layer are analyzed. The results show that the oxyacetylene surfacing are adopted as the welding method of hardfacing with cobalt-base alloys.The different nozzle diameters and preheating temperatures have an effect on the chemical composition,hardness and microstructure of the hardfacing layer. The main microstructure of the hardfacing layer is dendritic crystal. The larger nozzle diameters,the more dendritic crystal,the greater probability of secondary dendritic crystal formation. The grain size of hardfacing layer grows up and intragranular precipitation phase increases when the preheating temperature increases.