A systematic study of CO adsorption on the Fe(111) surface at different coverage is carried out with density functional theory. At 1/3 and 1/2 monolayer (ML) coverage, the shallow-hollow adsorption is the most stable site, while both shallow-hollow and bridge adsorption can coexist at 1 ML. Energetically, the bridge site rather than the suggested deep-hollow represents the reasonable adsorption configuration. In contrast, bent CO on-top and triply capping adsorptions are the most favored forms at 2 ML. The binding mechanism of CO on the Fe(111) surface is also analyzed. (C) 2004 Elsevier B.V. All rights reserved.