Organic-inorganic　hybrid　silica　membranes　modified　with　trifluoropropyl　groups　were　synthesized　by　acid-catalyzed　co-hydrolysis　and　polycondensation　reaction　of　(3,3,3-trifluoropropyl)　trimethoxysilane　(TFPTMS)　and　bridged　silsesquioxane　1,2-bis(triethoxysilyl)　ethane　(BTESE)　as　co-precursors.　The　effect　of　trifluoropropyl　groups　on　the　sol　particle　size　and　the　hydrophobic　property,　the　hydrogen　permeation　and　separation　behavior　and　the　hydrothermal　stability　of　the　obtained　membranes　were　investigated　in　detail.　The　results　show　that　trifluoropropyl　groups　have　been　successfully　incorporated　onto　the　surface　of　membranes.　The　sol　particle　size　decreases　gradually　and　hydrophobic　properties　of　the　modified　silica　membranes　are　enhanced　with　increasing　amount　of　TFPTMS　in　the　mixture.　When　the　molar　ratio　of　TFPTMS/BTESE　increases　to　0.6,　the　organic-inorganic　hybrid　silica　membranes　exhibit　water　contact　angles　of　111.6　degrees　+/-　0.7　degrees　and　a　narrow　sol　particle　size　distribution　centered　at　2.11　nm.　The　transport　of　hydrogen　in　the　modified　hybrid　silica　membranes　complies　with　a　micropore　diffusion　mechanism,　with　a　high　hydrogen　permeance　of　8.86x10(-7)　mol.m(-2).s(-1).Pa-1,　a　H-2/CO2　permselectivity　of　5.4,　and　a　H-2/CO2　binary　gas　(molar　ratio=1　:　1)　separation　factor　of　4.82　at　300　degrees　C,　higher　than　the　corresponding　Knudsen　value　(H-2/CO2=4.69).　The　modified　organic-inorganic　silica　membranes　are　hydrothermally　stable　while　aging　at　a　humid　atmosphere　with　a　temperature　of　250　degrees　C　and　a　steam　concentration　of　5%　for　more　than　300　hours.