WO3 nanorod arrays (WNRs) were synthesized on indium tin oxide conducting substrates by hydrothermal method. The effects of preparing conditions such as the precursor solutions concentration (H+ and Na2WO4), the additive NaCl, growth temperature and reaction time on the morphologies of WNRs have been systematically investigated by scanning electron microscopy, X-ray diffraction, Raman spectrum and ultraviolet visible absorption spectrum. It is shown that the pH value of the precursor solutions plays an important role in determining the morphology of as-prepared WNRs, which leads to different band gap energies. The orientation, density, and crystallinity of WNRs can be controlled by changing the amount of additive NaCl, Na2WO4 concentration and reaction temperature, respectively. Moreover, the growth mechanism of the WNRs was also discussed. (C) 2013 Elsevier B.V. All rights reserved.