The　adsorption　of　CO　on　regular　and　defect　sites　of　MgO(001)　surface　has　been　studied　theoretically　using　embedded　cluster　models　by　DFT/B3LYP　method.　The　value　of　embedded　point　charges　is　determined　by　the　charge　self-consistent　technique.　The　calculated　results　indicate　that　CO　adsorption　energy　on　the　regular　site　of　MgO(001)　surface　can　agree　well　with　the　recent　experimental　data.　The　frequency　shifts　of　CO　for　regular　five-coordinated　terrace,　low　four-coordinated　edge　and　three-coordinated　corner　sites,　via　C　bound　down　on　cationic　centers　of　MgO(001)　surface　are　also　satisfactorily　close　to　the　values　of　experiment.　At　the　same　time,　the　adsorption　of　CO　on　MgO(001)　surface　with　neutral　and　charged　oxygen　vacancies,　F-s,　F-s(+)　and　F-s(2+)　centers,　has　been　investigated　whose　results　show　that　MgO(001)　surface　with　neutral　oxygen　vacancy　has　probably　the　good　catalysis　structure　for　CO　adsorptive-decomposition.　This　is　consistent　with　our　previous　study　using　a　different　method.　By　analyzing　the　bond　component　of　Mg-C,　it　is　found　that　the　essential　reasons　why　C-O　bond　strength　is　weaken　or　strengthen　are　the　competitive　results　of　4sigma*　lone　pair　electrons　and　5sigma　electrons　of　CO　transferring　from　the　adsorbate　to　substrate　simultaneously.　(C)　2002　Published　by　Elsevier　Science　B.V.