Boehmite and boehmite-GPTMS hybrid membranes were fabricated on porous alpha-alumina support tubes using boehmite nanofibers for selective water separation from a liquid H2O/IPA mixture. The average sizes of the boehmite nanofibers were ca. 4 nm in width and ca. 1,200 nm, 1,400 nm and 2,000 nm in length. The influence of preparation conditions on the dehydration performance of the composite membranes was examined. As a result, the nanofiber membranes showed the higher separation performance when the withdrawal velocity of the alumina support tube was below 100 cm/min. The separation performance also increased with the number of coatings. Boehmite nanofibers of 1,200 nm and 1,400 nm in length were oriented in the lengthwise direction on the porous alumina support tube and formed slit-shaped micropores in the coated layer. Moreover, the separation factor was increased significantly to 1,628 by the hybridization with GPTMS, and the permeation flux was 0.88 kg.m(-2).h(-1).