The heatless desiccant air dryer is a kind of equipment for drying compressed air based on the principle of pressure swing. It absorbs moisture in the compressed air under pressure to dry the compressed air and use a part of dry compressed air to purge the adsorbent during decompression, so that the adsorbent can be regenerated；The two towers alternate with each other and are recycled to obtain dry compressed air. Different adsorbents can be selected according to the pressure dew point of the compressed air. Commonly used adsorbents include active alumina, molecular sieve, etc.