Radiation induced grafting of styrene/divinylbenzene onto radiation crosslinked F 46 films in the gaseous phase was carried out to develop the radiation induced grafting technique and improve the quality of obtained F 46 ion exchange membranes. The radiation crosslinking process was conducted under following conditions: Dose 3×10,6, rad to 7.5×10,9, rad; temperature, 200~230℃; and the pressure 4 pa. and 10,-3,~10,-5, pa. Thus obtained crosslinked F 46 films have a tensile strength of 180~240 kg/cm,2,. After annealing the radiation crosslinked F 46 films were irradiated again with dose about an order of magnitude less than, that for crossinking Results indicated that the crosslinked F 46 films brought about the increase of melting point, and after which a high elastic region was observed. Furthermore, grafting in gaseous phase caused less homopolymer in the system, and the quality of obtained F 46 ion exchange membranes might be improved. At the same time, the consumption of monomer was much decreased.