Abstract: The effect of nuclear radiation on dielectric properties of epoxy TDE-85/glass fiber E composite and bismaleimide 4501A/glass fiber D3W composite was studied in oxygen ambience using accelerated aging mothed. After samples were irradiated by ⁶⁰Co -rays at a range of dose 50~800kGy in air, the dielectric loss and dielectric permittivity of materials were measured using wave-guide method at 10GHz. It was found that the dielectric loss and dielectric permittivity increases with radiation dose, but increasing is not much, and the antiradiation property of 4501A/glass fiber D3W composite is better than that of TDE-85/glass fiber E composite. The change reasons of the dielectric property were analyzed using infrared (IR) and dynamic thermo gravimetric analysis (TGA) .