BaO-TeO2 thin films were prepared from tellurium(VI) alkoxide by a sol-gel method and their structure was investigated by X-ray diffractometry, Fourier transform infrared spectrometry, and 125Te static nuclear magnetic resonance. Their crystallization temperature (T-c), optical transmittance, and dielectric constant were measured, and their refractive index was calculated from the transmission spectra. The results indicate that the BaO-TeO2 thin films were composed of TeO6 and TeO4 units, and had a T-c of similar to 520 degrees C, refractive index of similar to 1.79, dielectric constant of similar to 20. These films had a T-c higher than the glass prepared by a melt-quench method, but their refractive index and dielectric constant were lower. These differences may be due to differences in their structural units.