Abstract: A two stage radiant cooler applied in compound-refrigerating system（CRS） was developed.The CRS radiant cooler could provide 8.5 W cooling power in the temperature of 194 K.and the refrigeration capacity of the cooler met the requirement of compound-refrigerating system.In this paper,the processes of structure selection,thermal design,optimize design and thermal/vacuum test were described in detail.Mont Carlo method was applied in the calculation of radiant interchange factor and the calculation error was less than 0.4%.Through optimize design,the working performance of the optimized radiant cooler almost kept no change,though the structure dimensions decreased greatly.The optimize design method based on the non-scale heat theory and numerical calculation was proved to be effective.