A new type microporous polypropylene film was prepared simply by biaxial drawing of beta-crystalline phase polypropylene. The effect of draw ratio on the pore size distribution, ethanol sorption, and porosity, as well as beta-alpha transformation during drawing were studied. For the purpose of improving its hydrophilicity, ion and solute permeability, the plasma graft-polymerization technique was utilized. The resulting film showed much higher permeability toward Na+, Mg++ and urea, being 3.2 x 10(-6), 5.8 x 10(-8) and 1.75 x 10(-6) cm(2)/min, respectively, than the original one and had better dimensional stability.