The CuO/CeO 2 catalysts are prepared by an improved incipient wetness impregnation method with ammonia as chelating agent for CO preferential oxidation (PROX). The effects of CuO loadings of the catalysts and the presence of H 2 O and CO 2 in the reaction stream on the catalytic performance are investigated. The CuO/CeO 2 catalyst with 10.0wt.% CuO loading has high activity and stability for the CO-PROX. In the long-term stability test under the realistic reaction condition with 10% H 2 O and 15% CO 2 in the reactant stream, 100% CO conversion can maintain for 1600h at 140–150°C with 85–75% selectivity. The catalysts are characterized by means of XRD, H 2 -TPR, and CO-TPR. The results show that the high activity of the CuO/CeO 2 catalyst is closely related to the fine-dispersed CuO species strongly interacting with CeO 2 support.