Palladium-alumina membrane with mesopore and narrow pore size distribution was prepared by the sol-gel method. Effect of the finely dispersed metal on the microstructure and the characteristic properties of the palladium-alumina membrane were investigated. Observations were made on membrane weight loss, morphology, pore structure, pore size, surface area, pore surface fractal and membrane's crystal structure. Autosorb analysis, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) analysis were employed in the membrane characterization. Autosorb analysis found that, BET surface area decreased and pore size of the membrane increased with the increasing of calcinations temperature (500-1100 degrees C) and with the increasing of palladium amount in the membrane. FTIR and TG/DTA analysis show that the suitable temperature for calcinations of palladium-alumina membrane is at 700 degrees C. Palladium metals are highly dispersed at calcinations temperature of 700 degrees C as observed by TEM analysis. The fine crystallinity of the palladium and gamma-alumina phase was obtained after calcined at 700 degrees C. The SEM morphology shows a smooth and free crack layer of palladium-alumina membrane after repeating the process of dipping, drying and calcinations at temperature of 700 degrees C. The membrane also successfully coated with a good adhesion on support. The thickness of the final membrane layer was estimated as 9 mu m. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.