The　waste　slag　of　aluminum　factory　composed　of　crystalline　γ-A1OOH　and　amorphous　solid　was　calcined　at　450,　600,　800,　1000,　1100,　1200　and　1300　°C,　respectively,　and　the　changes　of　crystalline　phase　at　different　temperature　can　provide　us　suitable　data　for　its　comprehensive　applications.　Their　polycrystalline　structures　and　microstructures　were　characterized　by　XRD　and　SEM　techniques.　The　crystalline　phases　of　the　waste　slag　were　changed　as　the　increasing　of　calcining　temperature:　(Equation　is　presented).　It　is　different　from　our　process.　Both　γ-Al2O3　and　amorphous　solid　were　formed　in　the　samples　at　600,　800　and　1000　°C.　The　contents　of　γ-Al2O3　and　amorphous　solid　decrease　with　the　rise　of　calcining　temperature,　and　they　are　completely　transformed　into　α-Al2O3　when　the　temperature　increased　up　to　1200　°C.　γ-Al2O3　was　metastable　phase　with　high-activity　while　α-Al2O3　was　stable　phase　with　low-activity.