Ethylene-propylene-diene terpolymer (EPDM) has been an important material in high voltage cable accessories which are connected to the superconducting power system. The dielectric properties are a great concern for the cable accessories. Doping of carbon black (CB) nanoparticles into EPDM has the effects of improving the insulating properties compared with undoped material. However, the effect of low temperature below 0°C has not been completely researched. In this paper, the samples were prepared by mixing CB nanoparticles into EPDM, with the content of 0, 1 and 5 wt% respectively. The experiment temperature was set to be −20, −40 and −60 °C. Relative permittivity and AC conductivity were measured with a 1 kV voltage at the frequency of 0.5∼1000000 Hz. The experiment results indicated that both nanoparticles and low temperature will affect the dielectric properties.