The hydrolysis process was investigated for AIN powder oxidizing treatment at high temperature in air. Samples were characterized by chemical analysis, XRD, and IR analysis. It was found that the hydrolysis of AIN powder in aqueous suspension was strongly dependent on the oxidation temperature. The rate of hydrolysis decreased as the oxidation temperature increased. A significant improvement in water resistance was observed when the powders were treated in air above 800 degrees C. The Al2O3 film formed by the oxidation treatment on the surface of AIN particles inhibits the reaction between AIN and water, thereby minimizing hydrolysis.