Abstract: In recent years,the low temperature refrigerator with reverse Brayton cycle has been widely concerned for its high efficiency,high reliability,fast refrigeration speed and wide range of refrigerating temperature.In this paper,a test rig of cryogenic reverse Brayton air refrigerator is newly built,in which performances of the refrigerator together with the components could be tested.The test rig is divided into the air supply part,refrigeration part and measurement part.The system cooling performance,thermal and mechanical characteristics of turboexpander,heat and mass transfer characteris-tics of regenerator,and food freezing characteristics can all be studied on the test rig.It can be used as a reference for re-search on cryogenic reverse Brayton refrigerators with working fluids of hydrogen and helium.Preliminary experimental study was carried out on the thermal performance of turboexpander at room temperature.The outlet temperature of the ex-pander could drop more than 33℃within 2 minutes under the expansion ratio of 2.15.The main diameter of rotor for the turboexpander was 10.00 mm,which was developed and designed independently.The turboexpander was supported by bump foil gas bearing,the maximum rotating speed was 278 kr/min and the isentropic efficiency reached 65.5%.The ex-perimental results showed that the cryogenic reverse Brayton air refrigerator has excellent thermal performance and cooling characteristics,which laid a foundation for the following research.