The CuO/CeO2 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 H2O and CO2 in the reaction stream on the catalytic performance are investigated. The CuO/CeO2 catalyst with 10.0 wt.% CuO loading has high activity and stability for the CO-PROX. In the long-term stability test under the realistic reaction condition with 10% H2O and 15% CO2 in the reactant stream, 100% CO conversion can maintain for 1600 h at 140-150 degrees 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/CeO2 catalyst is closely related to the fine-dispersed CuO species strongly interacting with CeO2 support. (C) 2010 Elsevier Ltd. All rights reserved.