Through the impregnation method, Ag catalysts with different support (such as TiO2 and γ-Al2O3) were prepared and then tested for catalytic oxidation of formaldehyde (HCHO) at low temperatures. The Ag/TiO2 catalyst exhibited strong catalytic performance, converting HCHO to CO2 and H2O at around 95°C. However, the Ag/Al2O3 catalysts showed much lower activity and reached？100% conversion at 125°C. The Ag-based catalysts were next characterized by several methods (XRD, TEM, FT-R, BET and H2-TPR). Results of characterization revealed that support dramatically impacts？the size and dispersion of Ag particles. The XRD analysis showed the existence of different peaks of the silver on the surface of Al2O3 in the contrast with TiO2 no specific peaks exist. Therefore, the size of the Ag particles and their dispersion are the most important factors that affect their catalytic performance for formaldehyde oxidation. In terms of catalytic performance for HCHO oxidation, the Ag/TiO2？catalyst possesses the best Ag dispersion, as well as the smallest Ag particle size.
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