The　adsorption　Of　O-2　at　oxygen　vacancy　site　(F,　F+　or　F2+　site)　and　magnesium　vacancy　site　(V,　V-　or　V2-　site)　has　been　studied　using　cluster　models　embedding　in　a　large　array　of　point　charges　coupled　to　density　functional　method　at　B3LYP/6-31G　(　d)　level.　The　value　of　point　charges　is　determined　by　the　self-consistent　technique.　The　calculated　results　indicate　that　the　MgO　(00　1)　surface　with　oxygen　vacancies　has　more　excellent　catalyst　structure　contributing　to　the　adsorptive-decomposition　Of　O-2　in　comparison　with　the　low-coordinated　corner　site　in　the　previous　study.　The　adsorption　energies　for　O-2　adsorbed　on　MgO(001)　surface　with　oxygen　vacancies　are　larger　than　those　on　MgO(001)　surface　with　magnesium　vacancies.　Moreover,　the　MgO(001)　surface　with　magnesium　vacancies　hardly　exhibits　catalytic　reactivity　toward　O-2　decomposition.　The　Mulliken　charge　analysis　illustrates　that,　for　O-2　adsorption　on　MgO　(001)　surface　with　oxygen　vacancies,　the　electrons　are　transferred　from　the　substrate　to　the　adsorbed　O-2　and　occupy　the　anti-bonding　orbital,　pi*　Of　O-2.　Thus,　the　O　-　O　bond　strength　is　weakened.　Potential　energy　curve　shows　that　the　energy　barrier　is　considerably　decreased　for　O-2　adsorbed　at　oxygen　vacancy　site　of　MgO(001)　surface　when　compared　to　that　at　corner　site　in　our　previous　study.