In this paper, the effects of γ-ray radiation on the electrical and mechanical properties of vulcanized silicone rubber used for spacecraft encapsulation are studied. The internal state of the silicone rubber before and after γ-ray irradiation and evolution mechanism is explained. The flame retardant characteristics, harmful gas emission and antibacterial properties of silicone rubber for space station and manned cabins are illustrated. The results show that the infrared characteristic peaks and thermal decomposition temperature remain generally unchanged after irradiation, while the electrical insulation becomes strengthened. With the increase of radiation dose, the tensile strength first increases and then decreases, the elongation at break decreases gradually, and hardness increases and then becomes stable. This paper expounds the cause of these phenomena respectively. Attention should be paid to vertical combustion characteristics and resistance to certain bacteria in application of manned cabins. The research provides instructions and guidance for engineers to select vulcanized silicone rubber in spacecraft.