The direct reaction method has been used for the fabrication of Al-Mg/Al₂O₃functionally gradient materials. It was found that the reaction layer of the Al-Mg/Al₂O₃powder compact at 900℃ under air atmosphere led to the formation of reaction layers with varying ceramic phase contents. As the results of experiments by using the TGA system, the characteristics and growth behavior of the reaction layers were affected by the reaction temperature, the gas flow rate, the Mg contents and the Al₂O₃contents.