The adsorption properties of CO on the nondefective and defective (with an oxygen vacancy) B-layer Fe3O4(0 0 1) surfaces (an octahedral environment of iron ions) at different coverages are studied using the spin-polarized density functional theory with the inclusion of on-site Coulomb interaction by introducing Hubbard U parameter (DFT + U) method. It is found that the CO adsorption energy in general increases with the CO coverage. Both types of B-layer Fe3O4(0 0 1) surfaces have the excellent ability for CO oxidation. Comparatively, the defective B-layer Fe3O4(0 0 1) surface has a much stronger CO adsorption ability and a lower CO oxidation ability than the nondefective B-layer Fe3O4(0 0 1) surface. The density of state reveals the bonding mechanism of CO on the two surfaces. The effects of the ambient conditions on the CO adsorption processes are analyzed. (C) 2014 Elsevier B.V. All rights reserved.