Abstract: Using pure tungsten as target,WO₃ thin films were prepared on glass substrate by DC reactive magnetron sputtering.Its crystal structures were analyzed by X-ray diffraction（XRD） method.The deposition technology of the WO₃ thin film was obtained.Electrochromism device of WO₃/ITO/Glass was prepared and its properties were studied.The experimental results showed that the transmissivity of the WO₃ thin film changed about 50% after the Li ions in jection.The device has a preferably reversible electrochromism performance,about 25% of W⁶⁺ in the WO₃ thin film change to W⁵⁺.