The　adsorption　of　ethylene　on　FeO(100)　surface　has　been　studied　with　a　periodic　slab　model　by　PW91　of　GGA　within　the　framework　of　the　density　functional　theory.　The　calculated　results　indicated　that　ethylene　adsorption　on　the　surface　hollow　site　forming　double　σ　bonds　was　the　most　favorable　structure　with　the　predicted　adsorption　energy　of　86.8　kJ/mol.　The　analysis　of　density　of　states,　charge　population,　orbitals,　and　vibrational　frequencies　before　and　after　the　adsorption　showed　that　Fe　2d　electrons　donated　to　the　anti-bonding　π　orbital　of　ethylene　and　the　adsorbed　ethylene　rehybridized　from　sp2　to　sp3　partly.