The CeO2-ZrO2-γ-Al2O3 nanocomposite was synthesized through the sol-gel route by mixing a boehmite sol (AlOOH) with an appropriate amount of metal nitrates. By using this multicomponent sol, crack and pinhole free mesoporous membranes were successfully fabricated on an asymmetric porous α-Al2O3 support through dip coating process. The hydrothermal (up to 75% steam) stability of the mesoporous membranes was studied in terms of hydrogen gas permeance at 500EC, phase structure, surface microstructure and pore size distribution. The pore size distribution measurements were conducted directly on the membranes by a nano-permporometer. Among the tested samples with different molar compositions of CeO2-ZrO2-γ-Al2O3, only the mesoporous CeO2-ZrO2-γ-Al2O3 membrane with a molar ratio of 10:10:80 mol% was found to be the most effective membrane under the hydrothermal condition at 500EC. The ternary CeO2-ZrO2-γ-Al2O3 system retained its structure (order and porosity) after crystallization on an α-Al2O3 porous support ...