Abstract: The bursting failure reasons of the final-stage superheater tube in a 600 MW ultra-supercritical boiler were analyzed through the methods of macro inspection, tensile test at room temperature, metallographic examination, hardness test, etc. The results show that the bursting tube experienced long-term overheating, the microstructure was seriously aged, and creep holes formed and connected to cracks, which finally resulted in the bursting at the weakest position of the elbow outside arc surface.