Electrochromic smart devices with controllable optical property are the most promising alternative to traditional windows and curtains. State of the art preparation and commercialization of large-scale electrochromic films are mainly based on vapor phase deposition, but massive application is limited by high price (due to complex preparation process). Here, an all-solution technology is developed for large-area low-cost preparation of electrochromic films. A WO3/ITO dispersion was successfully developed; high electrical conductivity ITO nanoparticle networks along with ITO coating on glass can serve as extended 3-dimensional electrode, which can form microelectrical field and act as the pathways for electron diffusion to WO3 nanorods. In fact, experiment results show that the surface resistance of WO3/ITO nanocomposite film decreased to 32% of the pure WO3. In other words, the optimum WO3/ITO nanocomposite films in this study with "distributed conductive structure" and submicrometer-sized voids morphology have improved the electrochromic properties remarkably. Our optimized WO3/ITO films exhibit higher optical modulation than pristine WO3 (Delta T = 81.7% vs 62.5% at 630 nm) and a faster switching speed (t(b) = 6 s vs 22 s).