The refrigeration dryer consists of heat exchange system, refrigeration system and electrical control system. The compressed air enters the precooler for air-to-air or air-to-cold heat exchange to remove part of the heat energy, and then enters the heat exchanger for heat exchange with the cold air cooled to the pressure dew point (2-119c) through the evaporator to further reduce the temperature of the compressed air. After that, the compressed air enters the evaporator for heat exchange with the refrigerant, the temperature drops to 2-11c, and the water in the air precipitates at this temperature