Abstract: The leakage failure of superheater happened in boiler No.1 of a power plant. Through chemical element analysis, macroscopic tests, microscopic metallographic analysis, and the quantitative measurement of the oxide scale on the inside-surface of the tube, in addition, by analyzing the thickness of the oxide scale on the inside-surface of the failed tube, the author evaluates the equivalent temperature and residual life time of the tube. Finally, the paper puts forward that the main reason leading to this failure is the long-term overheating of the tube. The preventive suggestions are also proposed.