WO3 nanoblocks were prepared by hydrothermal method on FTO glass, and WO3/Ag composite film was prepared by electrodepositing different content (20 s, 50 s, 80 s) of Ag nanoparticles onto WO3 nanoblocks. Characterization of WO3/Ag composite films was confirmed by X-ray diffraction analysis, scanning electron microscopy and energy spectroscopy. The parameters of electrochromic reversibility, response time, coloration efficiency and spectral transmittance were obtained by electrochomical measurement technologies and spectral tests. Then, the electrochromic properties were analyzed. The WO3/Ag composite films show the higher electrochromic properties compared with the WO3 nanoblock film. The effects of different Ag nanoparticle content on the electrochromic properties of WO3/Ag composite films were also studied. The results show that the WO3/Ag composite film deposited for 50 s has the best electrochromic properties.