Anodising industries produces large quantity of waste acid solutions containing high amounts of SO42-and Al ions.The work reported here is to synthesize high purity α-Al2O3 particles from waste anodic aluminum oxidation precursor solution via thermal decomposition of ammonium aluminum sulfate hydratewhich was fabricated by reerystallization at a reaction temperature of 60 ℃ with adjusting pH value of waste anodic aluminum oxidation precursor solution by adding appropriate amount of ammonia.Parameters during preparation process such as pH value of solution, order of recrystallization on precursor mass and product purity, calcining temperature on the crystalline structure and microstructure of alumina were studied, respectively.The as-obtained α-Al2O3 particles and their intermediate products were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), laser particle size analysis and thermal analysis (TG-DTA).Results indicated precursor solution pH value was corresponded to stoichiometric ratio of aluminum alum.When the pH value was 3.0 and crystallized time was twice, a relatively well dispersed ultrafine α-Al2O3powder (99.997% mass fraction) could be obtained after calcined at 1200 ℃ for 2h.The grains had short rod-like shape with 150nm in length and 100nm in diameter.This process has a large potential for industrial applications by synthesis of high purity Al2O3 with a simple and reliable technique.Waste anodic aluminum oxidation solution was utilized with great value and would significantly reduce the cost of chemicals used in the recovery.