Abstract: In this paper, the cellulose diacetate (CA) dense membrane, CA reverse osmosis (RO) membrane and cellulose triacetate (CTA) dense membrane were used for the separation of water-ethanol mixtures by pervaporation (PV). The effect of acetyl group contents and the membrane morphology on PV characteristics are discussed. For CA and CTA dense membranes, the total flux (J) and the water-ethanol selectivity coefficient (α) vary with feed compositions in the same way. But for all the feed compositions the J of the CTA dense membrane is slightly higher than that of the CA dense membrane. The J and α of the CA RO membrane vary with feed compositions in the opposite way as the CA dense membrane does.