The mechanical, electrical and heat resistant properties of 5229D/T700 conductive epoxy composites were systematically characterized. At the same time, the space environmental suitability of 5229D/T700 conductive epoxy composites was investigated by thermal vacuum outgassing test, thermal cycling test and total dose radiation test. The results show that the 5229D/T700 conductive epoxy composites has excellent heat resistance (T_g is 236℃, flexural strength retention is 85% at 150℃) and very low pollution (TML is 0.44%, CVCM is 0.05% at 150℃). It is also observed that the mechanical properties of conductive epoxy composites are hardly affected by thermal cycling and total dose radiation, while the electrical properties are slightly increased after total dose radiation, showing excellent space environmental suitability.