Abstract: Rigid hanger thread suspender of high temperature reheater influent header of an ultra supercritical 1 000 MW unit fractured. The fracture reasons were analyzed by macroscopic observation, chemical composition analysis, hardness test, room temperature tensile performance test, metallographic examination and fracture surface analysis. The results show that there was obvious necking phenomenon near the section of the threaded suspender, and there were creep holes on the whole section. The creep holes grew, aggregated and formed creep cracks. The measured temperature in the ladle on the top of the furnace greatly exceeded the original design value, and the calculated value of axial stress exceeded the standard under the measured temperature. Under the action of high temperature and high stress, creep fracture occurred at tooth root with stress concentration.