A very active catalyst of CuO/CeO2 was made by adsorption-impregnation method for preferential oxidation of CO in H2. The CO conversion is close to 100% and selectivity to CO oxidation is 96% over this catalyst at a low reaction temperature of 95 ℃ and a space velocity of 40000 cm3*g-1*h-1 in the reaction mixture of 1%CO, 1%O2, and 50%H2 balanced with N2. The effect of preparation conditions on catalytic performances was investigated. The catalytic performance of the CuO/CeO2 catalysts was compared with that of other CO preferential oxidation catalysts reported in literature.