Abstract: To meet the demand of radiation calibration for large diameter infrared measurement equipment,a low temperature point source blackbody system which diameter is 1.2 m is developed. The system consists of refrigeration unit and radiator two parts. Through the thermal load calculation to cool and heat system,cold and heat required is determined. At the same time,the temperature control system to ensure temperature uniformity are introduced. In order to test the temperature stability and uniformity of the system,a test device is built. The experimental results show that the temperature stability of the system reaches ±0.20 K,temperature uniformity reaches ±0.60 K,which can meet the design and practical requirements.