The hydrophobic and transparent SiO2-Al2O3 composite films were prepared by the sol-gel process using tetraethoxysliane (TEOS) and aluminium isopropoxide Al(C3H7O)3 as precursors, methyltriethoxysilane (MTES) and cetyltrimethylammonium bromide (CTAB) as chemical modifier and surfactant respectively. Optimum condition for the SiO2-Al2O3 nano-composite films with hydrophobic and transparent as well as mechanical properties simultaneously is investigated. It was found that the Si/Al molar ratio should be 1:0.008 and the calcined temperature should be 300°C. The infrared spectra of the films indicated that the hydrophobic surface of the film was due by the introduction of the methyl groups.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.