CuO-CeO2 catalysts were prepared by hydrothermal method. The influence of Cu loadings on the catalytic performance of CuO-CeO2 catalysts for the preferential oxidation of CO in excess H-2 has been studied and their physicochemical properties were characterized by X-ray powder diffraction (XRD), H-2-TPR, Ultraviolet-Raman (UV-Raman), Temperature-programmed surface reaction (CO-TPSR) and X-ray photoelectron spectroscopy (XPS) techniques. The results show that the 5.0 wt% CuO-CeO2 catalyst exhibits the highest catalytic activity, and the CO conversion achieves 99.6% at 130 degrees C. There are many forms of CuOx species, such as CuOx species strongly interacting with CeO2, the highly dispersed CuOx species on the surface of CeO2, and the bulk CuO or Cu+ species. Cu+ species on the CuO-CeO2 catalysts are advantageous to promote the catalytic performance indirectly. (C) 2008 Elsevier B.V. All rights reserved.