Abstract: In order to solve the problem of spontaneous combustion of residual coal in goaf caused by air leakage due to loose sealing at both ends during delayed mining. Taking 3302（lower） fully mechanized caving working face as engineering background, based on the analysis of the mechanical properties of fly ash ceramsite concrete, we obtain the optimal proportion of fly ash ceramsite concrete, and take it as the raw material for field application. The practice shows that the construction of the fly ash ceramsite concrete isolation wall is simple and fast, the O₂ volume fraction in the goaf eventually stabilized at about 10%, and the air leakage rate of the goaf is reduced from 20.6% to 4.9%, which reduces the natural possibility of the occurrence of residual coal in the goaf and ensures the production safety.