Various　hydrophobic　groups　were　used　to　modify　the　silica　membranes　by　the　co-hydrolysis　and　condensation　of　l,2-bis(triethoxysilyl)ethane　and　alkylsilanes.　The　hydrophobic　property　and　surface　roughness　of　silica　membranes　were　characterized　by　water　contact　angle　measurement　and　atomic　force　microscope,　respectively.　The　results　show　that　the　hydrophobic　property　of　modified　silica　membranes　increases　with　increasing　concentration　of　alkylsilane　in　the　mixture,　increasing　surface　roughness　and　increasing　length　of　carbon　chain　in　the　alkyl　groups.　©　(2014)　Trans　Tech　Publications,　Switzerland.