Aqueous precipitation and deposition-precipitation method were used to prepare CeO2 supports and Au/CeO2 catalysts, respectively. The effect of preparation condition of support on the catalyst activity was investigated. The catalytic combustion of HCHO was considered as the probe reaction for comparing the catalyst activity. The BET, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and Temperature-programmed reduction (TPR) were carried out to analyze the influence factor on the catalysts activity. The results showed that the addition of dispersant and use of microwave in the support preparation procedure could be beneficial for enhancing the interaction of supports and gold species and thus improved the catalytic activity. The total conversion temperature for HCHO was 146 °C over AC400. With the modification during supports preparation process, the catalytic activity increased with total conversion temperature decreasing to 98 °C. The results of XPS indicated that Au0 and Au+1 species coexisted in these catalysts and the activity of catalyst correlated with Au+1/Au0 ratio. Temperature-programmed reduction results demonstrated that the reduction peak appeared between 100-170 °C with the inducing of gold. The dependence of activity on the reduction peak temperature implied that ionic gold was catalytic activity component for HCHO oxidation.