Developing efficient, stable, and inexpensive catalysts for the preferential CO oxidation in H₂ (CO-PROX) over a wide temperature range in the presence of CO₂ and H₂O is indispensable for the hydrogen purification process. Herein, CuO was introduced to the CeMnO₂-supported Pt catalyst to modulate the oxygen activation capacity and provide the available number of active sites in CO-PROX. One part of the CuO species doped into CeO₂ strongly interacts with Ce, thus enhancing the oxygen transfer capacity of the catalyst. The other part of CuO species located on the surface of the catalyst provides extra Cu⁺ sites available for low-temperature CO adsorption. This synergistic interaction with Pt sites further enhances CO and O₂ activation, broadening the temperature window of high activity. The optimal Pt-10CuO/CeMnO₂ catalyst exhibits complete CO conversion (CO/O₂ ratio of 1:1) within the practical temperature range of 130–190 °C, even in the presence of CO₂ and H₂O, and remains stable at 150 °C for 76 h testing without any deactivation. This work will give a novel approach for the design of highly efficient inexpensive catalysts for industrial preferential oxidation of CO in H₂, especially in the presence of CO₂ and H₂O.