Abstract: A series of CuO/CeO₂ catalysts were prepared by impregnation method and used to preferential oxidation of CO in H₂-rich gas (CO-PROX). Catalytic performance with reaction temperature increasing or decreasing was studied to assess practical applicability of the catalysts. Phase composition and valence state change of the catalysts before and after CO-PROX reaction were analyzed by means of X-ray diffraction (XRD) and temperature programmed reduction (TPR) techniques. Formation of metallic Cu⁰ in the used catalyst was verified by XRD measurement. CO₂ in H₂-rich gas suppressed catalytic activity of the catalysts at the low reaction temperatures. A better catalytic performance for CO-PROX was observed on the catalyst with Cu/Ce atomic ratio at 10%.