First-principles　calculations　based　on　density　functional　theory　(DFT)　and　the　generalized　gradient　approximation　(GGA)　have　been　used　to　study　the　adsorption　of　CO　molecule　on　the　Cu2O　(lll)　oxygen-vacancy　surface.　Calculations　indicate　that　the　C-O　bond　is　weakened　upon　adsorption　compared　with　that　over　perfect　surface.　In　addition,　with　the　density　increase　of　the　defective　sites,　the　adsorption　energies　of　the　defect-CO　configuration　increase　whereas　the　C-0　bond　nearly　remains　constant.