Cu/CeO2 and CuO/CeO2, catalysts were prepared by solvated metal atom impregnation (SMAI) and conventional impregnation (Cl) and used for carbon monoxide oxidation in CO and air. The catalysts were characterized by means of XRD, XPS, AES and H-2-TPR techniques. The Cu/CeO2, catalyst prepared via SMAT exhibits higher catalytic activity in CO oxidation than that prepared via CI with the same Cu content due to the smaller Cu particles. The CuO/CeO2, catalyst prepared via SMAI also shows higher catalytic activity than that prepared via CI because the CuO particles of the former are smaller than the latter and can be reduced by CO more easily. The Cu/CeO2, catalysts display higher catalytic activities than CuO/CeO2, catalysts with the same Cu content and prepared by the same method. The TPR profile for CuO/CeO2, catalyst prepared via SMAI has a single peak, indicating a one-step reduction, whereas the TPR profile for CuO/CeO2, catalyst prepared via CI has two peaks, indicating a two-step reduction due to the existence of two kinds of CuO species.