We have been studying the addition of an ion-exchange group to commercial microfltration membrane(MF) of hollow fiber form by radiation-induced graft polymerization. But the pure water flux of the resulting hollow fiber was lower than that of the starting hollow fiber. To overcome the disadvantages, we suggest in this study a new mothod of cografting a reactive monomer with a cross-linking agent in place of cross-linking by radiation. A sulfonic acid(SS) group containing hollow fiber for MF was prepared by radiation-induced cografting of a monomer(GMA) with a cross-linking agent(nG,N-ethyleneglycoldimethacrylate) onto a microporous polyethylene hollow fiber followed by chemical conversion of the produced epoxide group to SS group.