Tungsten trioxide is an n-type semiconductor, which has been extensively used for the development of metal oxide semiconductor gas sensors. The hydrogen gas sensing performance of platinum (Pt) catalyst activated WO 3 thin films were investigated here. All of the Pt/WO 3 films membranes are sensitive to hydrogen gas and the sample by sol-gel and DC reactive magnetron sputtering methods. X-ray diffraction results indicate that the tungsten trioxide is cubic crystal, and the AFM analysis shows molecular structures of the samples are tetrahedron. It means the four consecutive quadrilateral forms we observed in the 9nmx9nm molecular structure are scattergram of tungsten-ions and oxide-ions on 106 sides in WO 2.9 structure cell, and the lost one oxide-ion resulted in the transition of WO 3 to WO 2.9 . With anneal temperature rising, the membranous poriness decreasing. The higher crystal degree is, the lower gasochromic efficiency is. The change of combining environment and content of O −2 ions in colorized / decolorized state WOx films was observed in XPS analysis of Pt/WO3 film, the peak shape had changed greatly. As a result, the explanation to this phenomenon is available here according to XPS chemical shift of electric potential model theory.