Abstract: The early burst failure of T91 heat resistant steel of a power plant boiler occurred. The coercivity of the material steel pipe was measured, and the microstructure aging and performance degradation were studied. The results show that during the aging process of the steel tube, the hardness of the material gradually decreased, the coercive force increased, and the aging of the material and the coercive force followed a certain functional relationship. Combined with the accumulated running time, inspection period and the change of coercivity of steel pipe, the remaining time of serious aging of steel pipe under service condition could be dynamically evaluated.