Polyimide-silica composite membranes were prepared by the sol-gel reaction starting from tetraethoxysilane(TEOS) in the solution of polyamic acid in N, N-dimethylacetamide(DMAc). The structural characteristics of the composite membranes were studied by scanning electron microscopy(SEM), thermogravimetirc analysis(TGA) and fourier transform infrared spectroscopy(FTIR). Single gas flux measurements for H₂, N₂, O₂, CO₂ and CH₄ were also obtained and the permeation results were discussed.