Iron doped TiO2 nanoparticles with different doping amounts were prepared using sol–gel method and characterized. These materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). Photocatalytic activities of the supported catalysts were examined for decolorization processes of methyl orange (MO) solution under UV irradiation. The results showed that doping of Fe3+ enhanced the photocatalytic activity of TiO2/HZSM-5, and the optimum Fe3+ doping of Fe/Ti mole ratio for TiO2/HZSM-5 was 0.07%. Doping of Fe3+ did not change the surface morphology of TiO2/HZSM-5. The Fe3+-doped TiO2/HZSM-5 possessed the anatase structures and Ti-O-Si bonds did not form between the HZSM-5 bulk and the supported TiO2.