The　adsorption　of　H2O　molecule　and　its　dissociation　products,　O　and　OH　on　CuCl(111)　surface　was　studied　with　periodic　slab　model　by　PW91　approach　of　GGA　within　the　framework　of　density　functional　theory.　The　results　of　geometry　optimization　indicate　that　the　top　site　is　stable　energetically　for　H2O　adsorbed　over　the　CuCl(111)　surface.　The　threefold　hollow　site　is　found　to　be　the　most　stable　adsorption　site　for　OH　and　O,　and　the　calculated　adsorption　energies　are　309.5　and　416.5　kJ/mol,　respectively.　Adsorption　of　H2O　on　oxygen-precovered　CuCl(111)　surface　to　form　surface　hydroxyl　groups　is　predicted　to　be　exothermic　by　180.1　kJ/mol.　The　stretching　vibrational　frequencies,　Mulliken　population　analysis　and　density　of　states　analysis　are　employed　to　interpret　the　possible　mechanism　for　the　computed　results.