Two types of composite films (MPC500SGF-MC and ANPSGF-MC) have been synthesized by a modified sol-gel method using different particle sizes of TiO2 powder. Methyl cellulose was added as a template to the sol for stress reduction which improved not only the amount of crystalline material immobilized on the support, but also the nanosize of the films calcined at 500°C. The physicochemical properties, including surface morphology, crystal size and adhesion on the glass substrate, were investigated by SEM and XRD. The photocatalytic activities of the films were compared using methyl orange (MO) as a model organic contaminant in water. The results on photocatalytic degradation of MO showed that the increase in photocatalytic activity for Aldrich TiO2 powder (ANP) calcined at 500°C, compared with that of Millenium PC500 composite film. The optimum degradation conditions of MO solution are determined. This study proves that particle size of starting TiO2 material is important for the preparation of nanostructure...