The　adsorption　and　dissociation　of　two　NO　molecules　on　Cu2O(111)　surface　have　been　studied　with　periodic　slab　model　by　DFT　method　using　the　generalized　gradient　approximation　(GGA)　with　the　Perdew-Burke-Emzerhof　(PBE)　exchange-correlation　functional.　Three　kinds　of　structures,　Cu+(NO)　(NO),　Cu+(NO)　(ON),　and　Cu+(ON)　(ON),　with　singlet　and　triplet　states,　were　considered.　Their　corresponding　adsorption　energies　and　Mulliken　charges　were　calculated.　The　calculated　results　indicate　that　in　the　optimized　Cu+(ON)(ON)　configuration,　two　adsorbed　NO　molecules　form　a　dimeric　species　with　a　much　shorter　N-N　bond　length(about　124.4　pm).　Such　a　configuration　contributes　to　the　dissociation　of　NO　to　Cu-O　surface　species,　with　elimination　of　N-2　or　N2O.