Abstract: Glass fiber reinforced epoxy resin(GF/EP) is used as support material for high energy physics and nuclear physics experiments due to its excellent thermal insulation and mechanical performance. High-energy physics and nuclear physics experiments produce large amounts of γ and neutron irradiation to the support material, while requiring GF/EP maintaining thermal stability as the support material. In this paper, the thermal properties including thermal expansion, thermal conductivity and thermal degradation of GF/EP under the γ irradiation of 20 kGy, 100 kGy and 200 kGy dosages were studied. The microstructure of GF/EP was observed before and after irradiation. The obtained results show that after irradiation, the microstructure of GF/EP changes, the matrix resin is fragmented, and the linear expansion range is narrowed with coefficient decreasing slightly. The thermal conductivity declines and the downward rate decreases with the increase of irradiation dosage, the thermal decomposition temperature is kept constant with the fastest thermal decomposition temperature droping slightly, the irradiation cross-linking and the irradiation degradation reaction occur simultaneously during the γ irradiation process, the overall thermal performance is stable with good stability within operating temperature range.