The　properties　of　BaTiO3　and　the　electronic　structure　of　H2O　adsorption　on　BaTiO3　were　investigated　by　using　first　principle　calculations　based　on　density　functional　theory.　The　calculated　results　show　that　the　orbital　hybridization　between　Ti　and　O　is　stronger　than　that　between　Ba　and　O.　With　the　increase　of　energy,　reflex　points　in　the　form　of　random　fluctuation　and　the　anisotropy　of　crystal　clear.　Enthalpy　and　heat　capacity　varies　with　temperature　rise,　while　free　energy　fall.　H　bonds　are　formed　between　the　hydrogen　of　water　and　the　surface　oxygen　of　BaTiO3　and　between　the　hydrogen　of　hydroxyl　and　the　surface　oxygen　of　BaTiO3.　The　adsorption　process　of　BaTiO3　adsorbing　H2O　is　a　physical　process　and　Delta　H　＜　0,　Delta　S　＜　0.