We prepared porous cation exchange membrane using polystyrene such as, EPS (expanded polystyrene), SAN (styrene acrylonitrile copolymer) and HIPS (high impact polystyrene). These three kind of polystyrene were sulfonated by acetyl sulfate to make sulfonated porous cation exchange membrane such as, SEPS (sulfonated expanded polystyrene), SSAN (sulfonated styrene acrylonitrile copolymer)and SHIPS (sulfonated high impact polystyrene). SEM was employed to validate porous structure of membrane, and IR spectroscopy was used to validate sulfonation rate of ion exchange membrane. As a results, ion exchange capacity was increased with an amount of sulfuric acid in reactants and cation exchange membrane showed the selectivity to a cation and showed the exclusivity to an anion.