The adsorption of CO molecule on the O-2 pre-adsorbed LaFeO3 (0 1 0) surface has been investigated using a density functional theory calculation. The calculated results show that the most appropriate reaction occurs between the CO and the pre-adsorbed O-2. After CO adsorption, the bonding mechanism between Fe site and the pre-adsorbed O-2 is not modified, and the HOMO-LUMO energy gap of the M1 mode is narrowed, which is caused by the redistribution of electron density in the surface. (C) 2011 Elsevier B.V. All rights reserved.