For the use requirements of spacecraft, a lightweight and highly efficient aerogel composite material with a density of less than 30 kg/m³ was developed. In the light of the application environment of deep space exploration, the thermal conductivity under different conditions, thermal cycling, thermal vacuum, and total ionizing dose experiment were conducted. The result shows that the service temperature of low-density aerogel composite covers -145~85°C and the thermal conductivity under 1 kPa CO₂ atmosphere can be as low as 6.6 mW/(m·K). The change law of thermal conductivity in different atmosphere and different temperature and different pressure in same atmosphere is studied. The thermal conductivity of aerogels from different batches is also tested, and the result shows that batch stability is good. The variation of the dimension and thermal conductivity after various thermal cycling and total ionizing dose experiment is zero,which indicates that low-density aerogel composite maintains good structure and stable thermal insulation in the deep space environment.