A series of FeO x - and Al 2O 3-supported Pt, Pd catalysts (0.23–2.1%) were prepared in this study. Pt/FeO x exhibited high CO oxidation activity with turnover frequency of 151 × 10 −3 s −1 (1% CO balanced with air, atmospheric pressure, 27 °C). A systematical study of FeO x - and Al 2O 3-supported Pt, Pd catalysts by means of X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, temperature-programmed reduction, H 2–O 2 titration, and time-resolved CO titration is reported. From 7% to 39% of Fe 3+ was reduced to Fe 2+ over Fe(OH) x -supported Pd and Pt catalysts, accompanied by Pd, Pt hydrogenation and hydroxyl loss, and a large amount of oxygen vacancies were proposed to be produced. Results of H 2–O 2 titration and time-resolved CO titration showed that a large amount of oxygen adsorbed onto FeO x support in the presence of Pt, Pd. This made CO oxidations over Pt/FeO x , Pd/FeO x proceed over two adjacent but different active sites (Pt, Pd for CO and FeO x for oxygen) with low apparent activation energies (30–34 kJ/mol), which accounted for their high activity in low-temperature CO oxidation.