Abstract: During fly ash concrete hardening process,the slow hydration of fly ash leads to low early strength of concrete,but can significantly improve the late strength of concrete(28d later),and also improve the heat resistance of concrete.In this paper,three kinds of curing ages including 28,56,90 d of the fly ash concrete specimens were used for the study,which naturally cooled after high temperature,it was analyzed the effect of curing age on the residual compressive strength,the residual splitting tensile strength,ultrasonic sound velocity and rebound value.