A novel organic dehydration membrane consisting of aminated polyacrylontrile (PAN) microporous. membrane as sublayer, alginate, coating as top layer has been prepared and characterized by pervaporation experiment. The influence of hydrolysis and amination of the microporous support layer on selectivity and flux was studied and it was shown that amination of the sublayer improved pervaporation performance of the composite membrane greatly. The counter cation of alginate coatings as dense separating layer also influenced separation properties of the membrane, which was better for K+ than for Na This novel composite membrane with K+ as counter ion has a high separation factor of 1116 and a good permeation rate of 350 g/m(2) h for pervaporation of 90 wt.% ethanol aqueous solution at 70 degreesC, higher separation factors and fluxes for n-PrOH/water, i-PrOH/water, acetone/water and dioxane/water systems. The results show that the separation factor and flux of this membrane increase with raising the operating temperature. At the same time, SEM micrographs show that the hydrolysis and amination of PAN microporous membrane change its pore structure. From the results it can be. concluded that pore structure of the sublayer in addition to its chemical structure also make influence of separation properties of the composite membrane.