SiO2 aerogel film was effectively silylated with n-hexane solution containing 6 vol.% of trimethylchlorosilane (TMCS). Through the silylation, hydrophilic polar -OH bond was exchanged with hydrophobic non-polar -Si(CH3) bond. Approximately 12% of reduction in dielectric constant and almost 2 orders of improvement in leakage current were observed after the silylation. Silylation behavior was examined with various volume concentrations of TMCS. The silylation of SiO2 aerogel film with 70% porosity was maximized when using 6 vol.% of TMCS. The fully silylated film showed an excellent moisture-resistant behavior. Even after 5 days of exposure to an air atmosphere with 45-50% of controlled humidity, an increase in dielectric constant due to the generation of polar -OH bond through moisture absorption was not observed. It was clearly revealed that the improved film properties such as low dielectric constant, low leakage current and high resistance to moisture absorption could be obtained by exchanging terminal polar -OH bond with non-polar -Si(CH3)(3) bond by the silylation with TMCS.