An inorganic Si-Al-C membrane is synthesized from pyrolyzing a polymeric precursor of polydimethylsilane and aluminum acetylacetonate supported on an alumina tube. The PMS + 10% Al-AcAc membrane, 773 K pyrolyzed, exhibits a hydrogen permeance 1.99 x 10(-9) mol Pa-1 s(-1) m(-2), H-2/N-2 selectivity 4.77, H-2/i-C4H10 selectivity 26.3 at room temperature, and H-2 permeance 6.57 x 10(-9) mol Pa-1 s(-1) m(-2), H-2/N-2 Selectivity 4.80, H-2/i-C4H10 selectivity 7.20 at 473 K. For the membrane pyrolyzed under a high temperature, its gas permeance is generally lower than those pyrolyzed at low temperatures due to pore sintering. Variations of permeation properties with respect to pyrolysis temperature could be interpreted from BET, infrared, and TGA/DTA data on PMS + Al-AcAc pyrolyzed residues.