The invention relates to a preparation method of a fleece-flower root swelling product, which comprises the following concrete steps: A, cleaning fresh fleece-flower root medicinal material, and chopping into particles with the size of 0.5-1.0 centimeter; B, heating the fleece-flower root particles of the step A at 50-60 DEG C, so that the moisture content is 10-20%; C, carrying out swelling processing on the fleece-flower root particle heated in the step B by a screw rod food extruding swelling machine, wherein the rotation speed of the swelling machine is 200-300r/min, and the swelling temperature is 120-150 DEG C, and obtaining the swelling product; and D, cooling the swelling product of the step C for 5-10 minutes, and packing. The method of the invention has simple operation and convenient processing, and the prepared fleece-flower root product has high bioavailability, loose texture, good taste, thick flavor and convenient taking.