Radiation-induced grafting of styrene onto polytetrafluoroethylene (PTFE) membranes was studied by a simultaneous irradiation technique. Grafting was carried out using γ-radiation from a ⁶⁰Co source at room temperature. Effects of absorbed dose, atmosphere, dose rate, and the concentration of initial monomer on the degree of grafting (DOG) were investigated and the most appropriate grafting condition was obtained. Subsequently, sulphonation of the grafted PTFE membrane (PTFE-g-PS) was carried out and a series of ion exchange membranes (PTFE-g-PSSA) was prepared. Further characterizations of FTIR, TGA, and SEM testified that grafting and sulphonation of the membranes were successfully processed; moreover, grafting of styrene not only occurred in the surface of PTFE membrane, but also in the micropores of the membrane. Ion exchange capacity (IEC) and conductivity were found increase with the grafting yield. The results suggest that at a low dose, such as 17 kGy, the ion exchange membrane (IEM) which will be suitable for vanadium redox battery (VRB) use can be obtained.