Using NH₃?H₂O and Al₂(SO₄)₃ as raw materials,the precursor of α-Al₂O₃ was prepared by spray-precipitation method. The nanometer α-Al₂O₃ powder with narrow distribution was obtained after washing,drying and calcining the precursor. The products were characterized by X-ray diffractometer(XRD),particle size analyzer and Fourier transform infrared spectrometer(FTIR). Results show that the product is α-Al₂O₃ powder,and its mean particle size is 30.9 nm,and its range of particle size is from 30.1 nm to 32.3 nm.