TiO 2 –SiO 2 films were successfully deposited on modified poly (ethylene terephthalate) (PET) substrate as one of the thermal-sensitive material with different content of SiO 2 . The as-prepared films were characterized with Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), respectively. At the ratio of Ti/Si=1:1, the TiO 2 –SiO 2 thin film showed the highest photocatalytic activity due to improving the ability of the surface adsorption and increasing surface hydroxyl group in the composite thin film. Moreover, the SiO 2 –TiO 2 composite thin film showed the most surface roughness, which further confirms the film with the highest photocatalytic activity at the ratio of Si/Ti=1:1. When the ratio of Si/Ti more than 1:1, the decrease in photocatalytic activity is due to reducing amount of the surface acidity sites and photocatalytic center.