The　adsorption　of　CO　on　regular　and　defect　sites　of　MgO(0　0　1)　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(0　0　1)　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(0　0　1)　surface　are　also　satisfactorily　close　to　the　values　of　experiment.　At　the　same　time,　the　adsorption　of　CO　on　MgO(0　0　1)　surface　with　neutral　and　charged　oxygen　vacancies,　Fs,　Fs+　and　Fs2+　centers,　has　been　investigated　whose　results　show　that　MgO(0　0　1)　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　4σ*　lone　pair　electrons　and　5σ　electrons　of　CO　transferring　from　the　adsorbate　to　substrate　simultaneously.　©　2002　Published　by　Elsevier　Science　B.V.