Cu-Ce/Al₂O₃ catalysts promoted with 3d-group transition metals have been prepared and tested for selective oxidation of CO in a H₂-rich stream. The effects of reaction temperature, process parameter(λ), promotor content upon both activity and selectivity have been investigated. Also, the presence of CO₂ and H₂O in the reactant feed on the activity and selectivity of catalysts were examined. Among the Cu-Ce based catalysts, Cu-Ce/Al₂O₃ promoted with 0.2 wt% Co gave the highest activity (>T₉₉) and selectivities(55-100%) under wide temperature windows(150-220℃).