Formulus and reaction conditions for the radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene were studied at room temperature in order to obtain higher molecular weight copolymer than those obtained in bulk or solution. It was found that ammonium perfluorooctanoate as an emulsifier is most suitable to obtain a stable latex of high molecular weight copolymer with good reactivity. The high molecular weight copolymer is obtained by using the emulsifier at high mole fraction of tetrafluoroethylene under the saturated vapor pressure of the monomer mixture. The molecular weight range of copolymers obtained in this experiment was from 3.0×104to 8×104, and these are higher than those obtained in bulk or solution.