Poly(3-hexylthiophene) (P3HT) was synthesized via chemical oxidative polymerization with anhydrous FeCl3 as oxidant, 3-hexylthiophene as monomer, chloroform as solvent. TiO2 nanoparticles modified by a small amount of P3HT (TiO2/P3HT) were prepared by blending TiO2 nanoparticles and P3HT in chloroform The resulting photocatalysts were characterized by the methods of TEM, XRD, FT-IR, XPS and solution. UV-vis diffuse reflectance spectroscope. The photocatalytic activity of TiO2/P3HT was investigated by degrading methyl orange under visible light. The degradation rate of methyl orange was 88.5 and 13.5% when it was degradated by TiO2/P3HT and neat TiO2(P-25) for 10 h, respectively. In addition. TiO2/P3HT nanocomposites showed excellent photocatalytic stability after 10 cycles under visible light irradiation. A possible mechanism for the photocatalytic oxidative degradation was also discussed. (C) 2009 Elsevier B.V. All rights reserved.