SrTiO3 thin films were deposited on vitreous ilica substractes by metalorganic decomposition (MOD). The films are polycrystalline cubic in structure with the lattice constants of a=0.39nm. their optical constants (refractive index n and extinction coefficient k) were calculated by the envelope method from the transmittance spectra in the wavelength range of 190nm to 1100nm. The refractive induex of the presnet films in found to be higher than that of the other SrTiO3 fims prepared by RF sputtering, sol-gel and chemical vapour deposition. The dispersion of the refractive index in the films follows the single electronic oscillator model with oscillator strength (S0) of 0.88×1014m-2 and oscillator energy (E0) of 6.40eV. The optical band gap of the films was estimated to be 3.68eV.