Size-controllable Ag nanoparticle ultrathin films, which were fabricated by vacuum deposition method from high purity Ag wire onto cleaned indium tin oxide conducting glass, have different color fabricated by variation of preparation conditions. The UV/Vis spectra showed that optical absorption peak of these Ag nanoparticle films can be tuned in a range from 457 nm to >650 nm. Scanning electron microscopy images showed that with increasing film thickness Ag particle size was larger. Ag/WO3 composite films were prepared by cathodic electrodeposition of WO3 onto the surface of Ag nanoparticle films. Spectro-electrochemistry and electrochromic properties of the resulting composite films were characterized. It was found that the electrochemical and electrochromatic properties of the composite films were adjustable with change the size of Ag nanoparticles in the composite films. Compared with a single component system of WO3, a substantial enhancement in the electroactive and electrochromic performance for the Ag embedded WO3 composite system was clearly observed. (C) 2009 Elsevier B.V. All rights reserved.