TiO2/SiO2 composite photocatalysts were prepared by depositing of TiO2 onto nano-SiO2 particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO2/SiO2 composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO2. Increases in the amount of TiO2 would decrease the dispersion in the composites. H2O2-sensitized TiO2/SiO2 composite photocatalysts could absorb visible light at wavelength below 550nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO2 exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO2 content over 30% decreased with increasing of TiO2 content. Increases in the calcination temperature and TiO2 content promote the formation of bulk TiO2 and result in a decrease in activity. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.