The WO3 semiconductor thin film was prepared on glass substrate by thermal evaporation techniques and a metal Pt layer was coated on the film surface. The structural analysis of the film was carried out using an X-ray diffractometer D5000 (Siemens). The hydrochromic properties of Pt-WO3 thin film at the wavelength range from 0.5 to 2.8 mu m in an atmosphere containing different hydrogen concentrations were investigated. The maximum sensitivity was observed at a wavelength of approx. 1.2 mu m by optical density measurement.