A　series　of　SO2-4/TiO2-SiO2　catalysts　with　different　mass　fractions　of　SiO2　were　prepared　by　solgel　method.　The　effect　of　adding　SiO2　on　the　crystal　structure,　specific　surface　area,　oxygen　adsorption,　and　acidity　of　SO2-4/TiO2　catalyst　and　its　photocatalytic　property　for　degradation　of　bromomethane　was　studied.　The　results　showed　that　the　specific　surface　area　and　amount　of　oxygen　adsorption　of　catalyst　were　increased　by　addition　of　SiO2,　leading　to　the　obvious　increase　on　photocatalytic　activity　of　SO2-4/TiO2-SiO2　catalysts　and　mineralization　ratio　of　bromomethane.　Comparing　with　SO2-4/TiO2,　the　acidic　strength　and　anti-moisture　ability　of　SO2-4/TiO2-SiO2　catalyst　were　decreased.