Bi-Si　mesoporous　molecular　zeolites　(Bi-Si)　was　synthesized　by　the　hydrothermal　method　with　ethyl　silicate　(TEOS)　as　silica　source,　Bi(NO3)3·5H2O　as　Bi　source,　and　cetyltrimethylammonium　bromide　(CTAB)　as　template.　Bi-Si　catalyst　had　high　ordering　structures　and　high　reaction　activity　in　oxidation　of　styrene　with　hydrogen　peroxide　to　benzaldehyde.　The　effects　of　solvents,　reaction　time,　reaction　temperature,　oxidant　concentration　and　Bi-Si　concentration　on　the　oxidation　of　styrene　to　benzaldehyde　were　studied　systematically.　It　was　found　that　in　the　following　reaction　conditions;　catalyst　0.075　g,　styrene　1.5　ml,　methanol　25　ml,　H2O2(30%)　4.5　ml,　T　=　80°C,　t　=　2　h,　the　conversion　of　styrene　was　43.1%,　the　selectivity　to　benzaldehyde　was　73.5%,　the　yield　of　benzaldehyde　reached　31.7%.　The　possible　reaction　mechanism　could　be　that　one　styrene　molecule　reacted　with　two　H2O2　molecules　on　two　joined　catalytically　active　sites.