Nanocrystalline titania films on titanium substrate were prepared by micro-arc oxidation in an electrolytic solution containing Na3PO4 and NaF. The process was carried out at high voltages and currents using a DC power supply. The crystal structure, chemical composition, surface morphology and optical property of the films were investigated by X-ray diffraction, X-ray fluorescence spectroscopy, scanning electron microscopy and UV-VIS spectroscopy, respectively. The photocatalytic activity of the films was evaluated by the decomposition of methylene blue. The relation between the concentration of NaF in the electrolyte and the property of the titania films was also discussed in the paper. (c) 2006 Elsevier B.V. All rights reserved.