A method for the acid (HCl or HNO3) dissolution of alpha-Al2O3 by MARS-5 microwave digestion system was proposed. When the temperature of digestion system increased to 240degreesC, alpha-Al2O3 sample was dissolved by HCl or HNO3, When the digestion reagent mass was constant, the digestion time was directly proportional to the sample mass. The digestion time was prolonged when the ratio of alpha-phase in Al2O3 sample was increased.