A series of vanadium oxide thin films with different layer thicknesses were prepared by the sol-gel process. These V2O5 thin films exhibited excellent gasochromic performance with color change from yellow to gray/black on exposure to hydrogen gas and fast response rate under ambient condition. The structure and morphology of the films were investigated by X-ray powder diffractometer and scanning electron microscope. The H-2 gasochromic property and the optical transmittance change of colored and bleached films were characterized by UV-visible spectrophotometer. Further, the gasochromic effect and the coloration mechanism of these films were investigated in detail by X-ray absorption spectroscopy. The investigations demonstrated that due to insertion of hydrogen ions, the valence state of vanadium varied from 4.8(+) to 4.1(+) and a distortion was observed in the structural symmetry of VO6 octahedron. (C) 2013 Elsevier B. V. All rights reserved.