Abstract: A new silicon membrane, which is employable in gas separation at higher temperature,is developed by control pyrolysis and activation of a thermosetting.silicon resin membrane. The chemical structure and composition, the conditions of pyrolysis and activation of the thermosetting silicon resin are the key factors which affect properties of the resulted silicon membranes. The molecular sieve silicon membranes have outstanding permselectivities as compared with common organic and inorganic membranes.The superiority of the silicon membrane is its higher heat resistance in comparison with carbon molecular sieve membrane.The silicon membranes also have a broad prospect to be applied in membrane separation of gas mixture at higher temperature.