Abstract: Carbon/epoxy composites (carbon fiber reinforced epoxy resin composites) have attracted a considerable attention on the utilization in space structures. The material properties and thermal-structural behavior are critical for understanding these structures. Thusly, thermophysical parameters of carbon/epoxy composites are investigated by thermophysical theories, finding that thermal conductivity coefficient and specific heat increase linearly with temperature rise. Moreover, a vacuum tank equipped with a heat sink and an infrared heating cage is utilized to simulate space thermal environment and to evaluate transient and steady temperature distributions on the thin-walled carbon/epoxy composite bar. Thermo-resistances and low-temperature strain gauges are employed to record time-history curves. The temperature and strain distributions in the longitudinal, transverse and thick directions under heat radiation conditions are obtained and analyzed in detail, which is significant for theoretical analysis, numerical simulations and structural design.