The nanocomposite films were prepared by direct intercalation of poly ( ethylene oxide ) and PEO into MoO3 xerogel via sol-gel route. The electrochromic behavior and the chemical conditions of Li + ions were investigated by cyclic voltammograms, UV-visible spectral transmittance and XPS. The results show that the cycling efficiency and the reversibility of insertion/extraction of Li+ ins in (PEO)1MoO3·nH2O nanocomposite film were improved. The intercalation of PEO into MoO3 xerogel modulated the wavelength range of electrochromism and enhanced the electrochromic efficiency. Two different chemical conditions of Li + ions existing in the interlayer and interstitial positions of MoO3 lattice were observed in MoO3 xerogel and (PEO)1 MoO3·nH2O nanocomposite films.