Niobium oxide thin films have been successfully fabricated on the indium-tin oxide coated glasses by pulsed laser deposition in an O-3/O-2 gas mixture. Films are characterized by X-ray diffraction and Raman spectrometry. Electrochemical and electrochromic properties of Nb2O5 films are examined by cyclic voltammogram and potential step coupled with an in situ charge-coupled device spectrophotometer. The unique characteristics of absorption spectra of Nb2O5 films are observed for the first time, and the optical absorption from the trapped electrons in the surface states plays an important role in the electrochromic phenomenon,