The design methods of the 20K large dimension cold shield based on Gifford-Mcmahon (G-M) cryocoolers used for infrared calibration test in space environment simulation test were introduced. The cold shield with 1m×1m boundary condition

the largest dimension in China

was cooled by five G-M cryocoolers. The installation and distribution of cold shield were introduced

and the method of compensator for contraction on cooling was also described in detail. The temperature distribution and cool-down time of cold shield surface were calculated and analyzed. The design of cold shield resolved the difficulty of compensator for contraction on cooling successfully. Test results showed that the temperature on the cold shield was 15K

and the temperature uniformity was ±1K. This indicated that the actual technical performance of the cold shield met and even exceeded the design requirements.