The catalysts of un-doped, single-doped and co-doped titanium dioxide (TiO2) nanoparticles were prepared by a sol-gel method with Ti(OC4H9)4 as a Ti source material. The photo-absorbance of the obtained nanoparticles was measured by UV-vis diffusive reflectance spectroscopy (UV-vis DRS), and the photocatalytic activity of the prepared samples under UV and visible light was estimated by measuring the degradation rate of phenol (50 mg/L) in an aqueous solution. The effect of Fe and La co-dopants on the material properties was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM)and N2 adsorption-desorption isotherm measurement. It was shown that the co-doped TiO2 could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions.The photocatalytic activity of TiO2 co-doped with Fe and La is markedly improved due to the synergistic actions of the two dopants.