Influence of preparation methods (i.e. co-precipitation, chelating, citric acid and critical phase) on the preferential oxidation of CO in excess hydrogen over CuO-CeO2 catalysts has been investigated. CuO-CeO2 catalysts are characterized by using BET, X-ray powder diffraction (XRD), UV Raman and temperature-programmed reduction (TPR) techniques. The catalyst prepared by chelating is most active for the preferential oxidation of CO. In addition, XRD, UV Raman and TPR show that the chelating method enhances the formation of defects of ceria and produces a synergic effect between the cycle of Cu1+/Cu2+ and that of Ce3+/Ce4+, which is beneficial to the improvement of the performance of CuO-CeO2 catalysts. (C) 2006 Elsevier B.V. All rights reserved.