The nickel-base alloy cladding and low alloy steel base material of tube-sheet were melted down owing to the abnormal heat input during seal welding between the heat transfer tube and the tube-sheet on a fabricating Steam Generator of a Nuclear Power Plant. Three potential repair schemes were proposed,and which were contrastively analyzed and evaluated from the aspects of operability,technical difficulty,leakage risk and in-service maintenance,etc. As a result,the temper bead welding scheme was determined and performed. Furthermore,the implementation schedule,procedure tests and results of the temper bead welding are introduced. The method of temper bead welding has been applied in engineering and can be used for the reference in dealing with similar cases in nuclear power engineering.