The　adsorption　and　dissociation　behaviors　of　water　on　the　UN　(110)　surface　have　been　investigated　by　using　DFT　+　U　method　in　combination　with　ab　initio　atomistic　thermodynamic　simulations.　The　most　stable　adsorption　site　for　H,　O,　and　OH　adsorption　is　the　uranium　bridge　site.　For　a　water　monomer,　the　adsorption　energies　are　-0.90,　-3.23,　and　-4.46　eV　for　the　most　stable　molecular,　partially　dissociative,　and　completely　dissociative　adsorption,　respectively.　The　dissociation　of　water　from　H2O　to　OH　and　H　has　a　very　small　energy　barrier,　while　from　OH　to　O　and　H　has　a　high　energy　barrier　of　1.63　eV.　The　coverage　dependence　for　molecular　adsorption　is　not　obvious,　while　for　partially　dissociative　and　completely　dissociative　adsorption,　the　coverage　dependence　is　quite　obvious.　Besides,　we　have　investigated　the　adsorption　of　water　under　different　temperature　and　pressure　conditions　by　using　the　＂ab　initio　atomistic　thermodynamic＂　method.　(C)　2017　Elsevier　B.V.　All　rights　reserved.