Alumina, Al2O3, films were prepared by the sol-gel process and deposited by spin coating technique. The coating solutions were synthesized by using aluminum-sec butoxide, Al((OBu)-Bu-5)(3), as a precursor, isopropanol as a solvent, acetylacetone, AcAcH, as a chelating agent and nitric acid, HNO3 as catalyzer. Highly transparent alumina coatings with thickness in the range of 100-700 nm were prepared at different spinning rates and heat treated at 400 degrees C. The morphology, microstructure, transmittance characteristics of the films were investigated. The investigations were performed by optical and Fourier infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). SEM examinations and spectrophotometric measurements show that the films were homogeneous and uniform with a visible light transmittance higher than 90 %. XRD of the alumina films heat treated at the temperatures below 500 degrees C showed that they had an amorphous structure. XPS examination showed that amorphous films were stoichiometric Al2O3.