The invention discloses a cleaning method for compact fly ash on an inner cavity wall of an ash discharging storeroom. The cleaning method is characterized in that an air cannon is used for jetting high-speed air flow into the ash discharging storeroom so that scattering operation can be carried out on the compact fly ash in the ash discharging storeroom, then, a soot blower is used for blowing the scattered fly ash so that the fly ash can restore the flowing state and can be discharged out of a discharging port of the ash discharging storeroom. The cleaning method has the beneficial effects that the compact fly ash can be cleaned away better, operation is convenient, and the automation degree is high.