A simple method was developed to fabricate tungsten oxide (WO3-x) nanowires based electrochromic devices. The WO3-x nanowires are grown directly from tungsten oxide powders in a tube furnace. The WO3-x nanowires have diameters ranging froin 30 to 70 nm and lengths Lip to several micrometers. The WO3-x nanowires based device has short bleach-coloration transition time and can be grown on a large scale directly onto ail ITO-coated glass that makes it potential in many electrochromic applications. The structure, morphology, and composition of the WO3-x nanowires were characterized using the scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive spectrometer. The optical and electrochromic performance of the nanowires layer under lithium intercalation was Studied in detail by UV-VIS-NIR spectroscope and cyclic voltameter. (c) 2005 Published by Elsevier B.V.