In this work, MnOx modified Co3O4-CeO2 catalysts were prepared and used for preferential oxidation of CO in hydrogen-rich gases. The catalytic performance tests results showed that the catalyst with Co:Ce:Mn molar ratio of 8:1:1 exhibited the best low-temperature CO oxidation activity and higher selectivity for CO-PROX reaction among tested catalysts. 100% CO conversion could be obtained over this catalyst at 80-180 degrees C with the feeding gas of 1 vol.% CO, 1 vol.% O-2, 50 vol.% H-2 and N-2 balance under the space velocity of 40, 000 ml h(-1) g(cat)(-1) Adding CO2 and/or water was unfavorable for CO removal, even so complete oxidation of CO was still achieved over this catalyst with the reaction stream of 20 vol.% CO2, 10 vol.% H2O, 1 vol-% CO, 1 vol-% O-2, 50 vol.% H-2 and N-2 balance under high space velocity of 80,000 ml h(cat)(-1) g(-1) at reaction temperature range of 160-180 degrees C. The catalysts were characterized by XRD, TEM, EDX, TPR and XPS techniques and the results showed that adding MnOx into Co3O4-CeO2 led to more uniform mixing of Co3O4 and CeO2 particles and led to finely dispersed and high valence state cobalt oxides species, which contributed to high catalytic activity of Co-Ce-Mn mixed oxides catalysts. (C) 2008 Elsevier B.V. All rights reserved.