Aluminum ash is an industrial waste residue produced during alumina electrolysis and aluminum processing and casting. In the experiment, alumina powder with a purity of 98.97% was prepared by sintering with sodium hydroxide and the process conditions affecting the dissolution rate of Al2O3 from aluminum ash were studied. The best process conditions for the dissolution of Al2O3 are the sintering temperature of 700°C, the alkali-ash ratio of 1.2:1, and the time of 2h using orthogonal experiments. The phases of the aluminum ash and alumina were determined by X-ray diffraction(XRD) analysis. The chemical compositions of the aluminum ash and alumina were determined by X-ray fluorescence (XRF) spectroscopy. The microstructure and morphology of the aluminum ash and alumina were studied with scanning electron microscopy (SEM). Alumina prepared can be used as a metallurgical material.