Abstract: The SiO₂-TiO₂ thin films were prepared by sol-gel dip coating.The crystallization of the films was thoroughly studied by X-ray diffraction（XRD）,Scanning electron microscope（SEM） and the nitrogen adsorption experiment.Furthermore the phase formation,microstructure and photo-catalytic activity of SiO₂-TiO₂ films heat treated at different temperatures were studied.It is found that with the addition of above 10% SiO₂,the phase transformation temperature of anatase to rutile increase.Studies on photo-catalytic degradation of methye orange show that when 10% SiO₂ is added to the TiO₂ sol-gel system at tempcrature heat theated above 500℃,the photo-catalytic activity of SiO₂-TiO₂ thin films is optimized.