Abstract: Bi-Si mesoporous zeolites(Bi-Si)with different Si/Bi ratios were synthesized with the hydrothermal method which used TEOS as silica source, Bi(NO₃)₃•5H₂O as metal source, cetyltrimethylammonium bromide as template, and the oxidation of styrene by hydrogen peroxide to benzaldehyde catalyzed by the zeolite prepared was investigated.The nature of the catalysts was discussed based on the characterization results with nitrogen adsorption-desorption (BET), X-ray diffraction(XRD), scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet-visible spectroscopy(UV-Vis),and thermogravimetric method(TG).Bi-Si had high ordering structures of Mobile Crystalline Material-41 and bismuth was highly dispersed in the mesostructure framework.With increasing bismuth content, the crystallite of Bi-Si became disorderly,and at the same time the value of d₁₀₀ decreased.Bi-Si was found to be catalytically active in the oxidation of styrene to benzaldehyde with H₂O₂ as oxidant and methanol as solvent.The conversion of styrene increased with increasing Bi content,while the selectivity of benzaldehyde decreased.The catalyst with Si/Bi=22.5(mole ratio) showed higher catalytic activity,and the yield of benzaldehyde reached 14.1%.The influence of the ordering of mesostructure and the Bi content on the oxidation activity of Bi-Si was also discussed.