Organic-inorganic　hybrid　silica　membranes　were　prepared　by　sol-gel　technique　using　1,2-bis　(triethoxysilyl)ethane　(BTESE)　and　1H,1H,2H,2H-perfluorooctyltriethoxysilane　(PFOTES)　as　precursors　under　acidic　condition.　The　hydrophobic　property,　sol　particle　size　distribution　and　pore　structure　of　the　modified　silica　membranes　were　characterized　by　contact　angle　measurement,　FT-IR,　dynamic　light　scattering　and　N-2　adsorption,　respectively.　The　hydrogen　permeation,　separation　and　hydrothermal　stability　of　the　supported　membranes　were　also　investigated　in　detail.　The　results　show　that　hydrophobic　microporous　membranes　are　obtained　after　modification　by　perfluorooctyl　groups,　with　a　water　contact　angle　of　(110.4　+/-　0.4)degrees　and　a　pore　size　ranging　from　0.5　to　0.8　nm　at　a　PFOTES/BTESE　molar　ratio　of　0.6.　At　300　degrees　C,　the　transport　of　hydrogen　in　the　modified　supported　hybrid　silica　membranes　complies　with　a　micropore　diffusion　mechanism,　with　a　high　hydrogen　permeance　of　8.5x10(-7)　mol.m(-2).s(-1).Pa-1,　a　H-2/CO2,　H-2/CO　and　H-2/SF6　permselectivity　of　5.49,　5.90　and　18.36,　respectively,　higher　than　those　of　the　corresponding　Knudsen　value.　Under　a　humid　condition　with　a　temperature　of　250　degrees　C　and　a　water　vapor　molar　ratio　of　5%,　the　hydrogen　permeance　and　H-2/CO2　permselectivity　of　the　modified　silica　membranes　remain　almost　constant,　indicative　of　an　excellent　hydrothermal　stability　for　the　membranes.