A gold catalyst Au/meso-?-Al2O3 was synthesized by depositing Au NPs onto a home-made mesoporous ?-Al2O3 via deposition-precipitation method for the CO oxidation. The preparation, drying and calcination conditions were systematically investigated, and the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), N2 adsorption isotherm at -196 oC, inductively coupled plasma atomic emission spectrometry (ICP-AES), and Uv-vis DRS. The experimental testing results indicated that the small Au NPs of ~2.0 nm is highly active for the CO oxidation, which could be realized by accurately controlling the preparation, drying and calcination conditions.