The　adsorption　of　NO　adsorbed　on　MgO(001)　perfect　and　defect　surfaces　has　been　studied　by　using　cluster　models　embedded　in　a　lot　of　point　charges(PC)　with　DFT/B3LYP　method　at　the　6-31G(d)　basis　set　level.　The　calculated　results　indicate　that　the　surface　with　various　oxygen　vacancies　has　the　high　catalytic　reactivity　for　NO　dissociation.　Besides,　it　is　found　that　the　NO　bond　will　be　broken　when　another　NO　molecule　approaches　the　adsorbed　NO　with　concurrent　production　of　N2O,　which　is　consistent　with　the　phenomenon　of　MIES　and　UPS　experiments.　Mulliken　population　analysis　shows　that　the　electron　transfer　from　the　substrate　to　the　anti-bonding　pi*　orbital　of　adsorbed　NO　is　the　essential　reason　for　the　weakening　of　NO　bond.　This　can　also　cause　the　production　of　NO-.　At　the　same　time,　the　MgO(001)　surface　with　magnesium　vacancies　exhibits　almost　no　reactivity　for　NO　dissociation.