In order to evaluate the radiation degradation of ethylene propylene rubber (EPR), radiation effects on EPR was investigated by using dielectric analysis and thermal-gravimetric analysis. Permittivity, loss factor, tan δ and thermal decomposition temperature were observed for γ-ray irradiated EPR. As radiation dose increased, the peak temperature of loss factor and tan δ of EPR increased, and loss factor and tan δ at peak temperature decreased. Activation energies were calculated using loss factor and thermal decomposition for g-ray irradiated EPR as well. The trends of both calculated activation energies showed same tendencies as radiation dose was increased.