Tungsten trioxide/reduced graphene oxide (WO 3 /RGO) nanocomposite film was fabricated by the sol-gel spin coating technique, using a mixed colloidal dispersions of WO 3 precursor and GO. The structure, surface morphology and optical properties of the WO 3 and WO 3 /RGO films were investigated by means of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, highresolution transmission electronmicroscopy and UV-visible spectrophotometer. The electrochemical and electrochromic performance of the WO 3 and WO 3 /RGO films were studied by chronoamperometry, in-situ optical transmittance and cyclic voltammograms analysis. In the WO 3 /RGO nanocomposite film, monoclinic WO 3 nanoparticles were grafted onto the surface of RGO sheets via C-W and C-O-W chemical bonds. The results showed that WO 3 /RGO nanocomposite film exhibited shorter coloration-bleaching times (t c = 9.5 s and t b = 7.6 s), higher coloration efficiency (75.3 cm 2 C -1 at 633 nm), larger optical modulatory range (59.6% at 633 nm) and better cyclic stability compared with WO 3 films, which are attributed to faster Li + ion diffusion and electron transfer rate. The methodology provides a facile and industrially scalable approach to obtain fast switching electrochromic materials.