The ammonium ion exchanged membranes were prepared with sulfonated polysulfone and their applications for dehydration of ethanol solution by pervaporation were investigation. The degrees of ammonium substitution in membranes were prepared by predetermined sulfonated polysulfone. The dependence on the hydrophilic properties of ion exchanged membrane on pervaporation performance and degree of swelling of membranes were investigated. The dependence of sulfonation on the pervaporation performance was discussed in this study. It was found that the ammonium substitution in hydrophobic polymer strongly enhanced the permeation flux and separation factor of pervaporation membranes. It is interesting to note that the water content in membranes not only affected the degree of swelling but also the pervaporation performance.