By a wide energy gap, tungsten-Oxide is a semiconductor with significant chromogenic features. This metallic oxide has also so many properties such as electrochromic and become applicable as photocatalyst and gas sensor. Among these properties, its chromogenic one in the presence of hydrogen gas is really significant. Nowadays, hydrogen as a clean and renewable fuel is considered as an alternative for fossil fuels for home, industrial and specifically in traortation consumptions. An important note in usage of this gas is its extreme flammability in range of 4 to 75 percent of combination with the air. Since tungsten-oxide change its color while being exposed to the hydrogen, we can use it as a hydrogen gas sensor. Through this thesis the colloid nanoparticles of tungsten oxide are produced by electrolysis approach. In order to make these nanoparticles sensitive to hydrogen, palladium catalyst is added to the solution achieved by electrolysis, with the concentration of . Nanoparticles powder of these samples was produced and it was tried to find their structures, chemical bounding and morphologies. The X-ray diffraction (XRD) spectrum determined the crystallographic structure of the sample and this analysis showed that the nanoparticles are tungsten-oxide dihydrate . Dehydration and formation of monoclinic was obtained By annealing these powders at and . Chemical properties of samples were studied by analysis of fourier transmission Infra-red (FTIR) and X-ray photoelectron spectroscopy (XPS). These analyses have shown the elimination of water molecules bounding and hydroxyl group from the sample and formation of completely oxide ones after the annealing process. The field-emission scanning electron microscope (FE- SEM ) pictures revealed the formation of plate-like morphology in some parts. Optical properties of the colloid solution was measured by spectrophotometer (UV-Vis) in range of . The effect of palladium concentration and the time of electrolysis on gasochromic process are shown significantly through its results and it is shown that application of specific amount of palladium would enhance the gasochromic process. Also, different absorption peaks were observed at and in the spectrum in the presence of hydrogen gas. Each of these peaks belonged to the specific color centers which are known as bulk paramagnetism, surface paramagnetism and surface diamagnetism respectively.