Bi-layer WO3 thin films were prepared onto ITO/glass substrates, where the lower layer was deposited by using DC sputtering and the upper nanotube layer by was grown by using anodization method. The influences of anode voltage on the growth of the nanotube WO3 thin films were investigated. The morphology and cross section observations of the bi-layer WO3 thin films were carried out by using FESEM. It was found that the 40V was the optimally applied voltage because WO3 thin films revealed the uniform porous nanotube and the diameters distributed from 30 nm to 56 nm with the average diameters of 40 nm. The electrochromic properties of the bi-layer WO3 thin films were also developed in this study under different volumes of LiClO4-PC solution.