Abstract: The platen superheater tube failures of T92 steel has bursted in a ultra supercritical power plants. The bursting reason was analyzed by means of macroscopical inspection, chemical composition analysis, hardness testing, tensile strength testing, metallographic examination and so on. Results showed that the microstructure of the tube which didn’t maintenance the typical lath martensite, the phase transformation at AC1~AC3 after short-term overheated. The strength decreased rapid distinctly, therefore the strength was not enough to endure the stress, finally the tube bursted. On the other hand, the relationship between the different microstructure and mechanical property was achieved by test in order to supervise for metal in thermal power plants for long term operation.