Abstract: The present application is related to a method for preparing a feeding instant Astragalus polysaccharide powder and an application thereof. The method includes the following steps: adding deionized water at 65° C. to a dreg of Astragalus membranaceus by water extraction and alcohol precipitation, controlling an alcohol volume fraction at 20%, stirring fully to dissolve the dreg, and after a dreg solution cools to room temperature, removing insoluble thermo-sensitive macromolecular proteins, polysaccharides and solid residues by centrifugation at 3500 revolutions per minute to obtain a clear supernatant. Ultrafiltration treatment is performed by hollow fiber membranes on the supernatant obtained after the centrifugation, and 10-100 kDa polysaccharide components are collected. A low-molecular-weight instant Astragalus polysaccharide powder with high immunocompetence is obtained through an interlayer cold air cooling spray drying process, and the content of active polysaccharide is more than 87%.