Nanocomposite of K0.3Ti4O7.3(OH)(1.7) fiber and anatase TiO2 nanoparticle was prepared by hydrothermal treatment of the K0.3Ti4O7.3(OH)(1.7) which was synthesized by calcination of K2CO3 and TiO2 at 1250 degrees C followed by refluxing in nitric acid. Effects of hydrothermal treatment conditions such as temperature and time on morphology, phase composition and crystal structure of the nanocomposites were extensively studied. Photocatalytic activities of the catalysts prepared at various hydrothermal conditions were evaluated by means of methylene blue decomposition under blacklight irradiation. (C) 2008 Elsevier B.V. All rights reserved.