Two types of mesoporous SiO2 membranes supported on the TiO2-deposited kieselguhr-mullite ceramic tubular substrates were prepared successfully by the method of combining sol-gel process with template technology. Dodecyl trimethyl ammonium chloride (DTAC), C12H25(CH3)(3)N+Cl-, was used as the template agent and tetraethoxysilane (TEOS) or Na2SiO3 was used as organic or inorganic silicon source. The techniques of SEM, TGA, IR, nitrogen absorption, and gas permeation test were used to characterize their properties. The results showed that the surface morphologies of both membranes are complete and defect-free, and the bond-linking structure has been formed between silicate and template agent. The SiO2 membrane prepared from TEOS has both crystalline phase and amorphous phase with average pore size of 4.2 nm and with the maximal organic decompose temperature of 297 degreesC, whereas the SiO2 membrane prepared from Na2SiO3 only has crystal phase with average pore size of 6.0 nm and the maximal organic decompose temperature of 275 degreesC. The gas permeability of both the supported membranes was controlled by Knudsen diffusion. (C) 2003 Elsevier Science B.V. All rights reserved.