Owing to the unique properties such as facile redoxability and high stability, ceria has been used for a wide range of applications including automotive emission control, catalytic combustion, hydrocarbon reforming, and electrocatalytic reactions. It is well known that enhanced chemical reactivity can be achieved on transition metal (TM)-doped ceria nano-catalysts. In particular, co-doping of TM on CeO2 surface has recently opened a great potential to improve the catalytic activity compared to the single doped one. In this study, we performed OFT calculations to compare the activity of CO oxidation between Mn-, Fe-, and (Mn,Fe)-doped CeO2(111) via Mars-van Krevelen (MvK) mechanism. We firstly verified that a conventional linear relationship between oxygen vacancy formation energy and the catalytic activity of CO oxidation is also effective for the co-doped CeO2(111). It turns out that the energy required to create oxygen vacancy (E-vf), that is a key descriptor of the reactivity, will be extremely useful to rapidly screen the catalytic activity on co-doped oxide system. Then, we investigated the entire reaction profile of CO oxidation via the MvK mechanism on Fe-, Mn-and (Mn,Fe)-doped CeO2(111). Based on the results, we confirmed the improved activity of CO oxidation on the co-doped system, which was in good agreement with the prediction from E-vf. From this study, we believe that the co-doping of TM on oxide catalysts will be a noble strategy to enhance the catalytic activity. (C) 2016 Elsevier B.V. All rights reserved.