Brown corundum dust ash(BCFA) is an industrial solid waste from the brown corundum production process. The alkali metal is a key factor limiting its comprehensive use. Currently, BCFA is mainly stockpiled and occupies a large amount of land. Its fine particles are easy to cause air pollution. The addition of NH4HSO4 allows for the effective extraction of K from BCFA and the efficient use of BCFA. Under optimum conditions: NH4HSO4 to BCFA mass ratio of 1.2:1, the roasting temperature of 240 ℃, roasting time of 2 h, water leaching time of 90 min, water leaching temperature of 65 ℃ water leaching liquid to solid ratio of 3:1, the leaching rate of K from BCFA reached 97%. The leachate was crystallised by evaporation to obtain K, N compound fertiliser for agricultural use. The leaching residue is mainly Al and Si, which can be used for the preparation of refractory materials, aluminium and silicon molecular sieves, construction materials and other raw materials.