The　density　functional　theory　(DFT)　and　periodic　slab　model　were　used　to　get　information　concerning　the　adsorption　of　HCHO　on　the　FeO(100)　surface.　A　preferred　eta(2)-(C,O)-di-sigma　four-membered　ring　adsorption　conformation　on　the　Fe-top　site　was　found　to　be　the　most　favorable　structure　with　the　predicted　adsorption　energy　of　210.7　kJ/mol.　The　analysis　of　density　of　states,　Mulliken　population,　and　vibrational　frequencies　before　and　after　adsorption　showed　clear　weakening　of　the　carbonyl　bond,　and　high　sp(3)　character　on　the　carbon　atom.