NOVELTY - Diosgenin is ultrasonic-extracted from leaves of Dioscorea zingiberensis and separated, to obtain powder containing starch and Dioscorea extracting liquid. The extracting liquid is precipitated, to obtain system (b). The starch flocculant is added to system (b), flocculated and separated, to obtain supernatant and floc (c). The obtained floc (c1) is pressed with sulfuric acid, hydrolyzed and filtered, to obtain residue (e). The residue (e) is washed, dried, and diosgenin is extracted using extraction agent, Soxhlet-extracted, cooled and crystallized, to obtain diosgenin.    USE - Extraction of saponin from D.zingiberensis (claimed).    ADVANTAGE - The method enables efficient and environmentally-friendly extraction of saponin from D.zingiberensis, with reduced chemical oxygen demand value, biological oxygen demand value and acid hydrolysis concentration.    DETAILED DESCRIPTION - Diosgenin is ultrasonic-extracted from leaves of D.zingiberensis and separated, to obtain powder containing starch and Dioscorea extracting liquid. The extracting liquid is precipitated by physical separation, and starch is removed, to obtain system (b). The starch flocculant is added to system (b) and stirred, to obtain flocculant precipitate. The system (b) is placed in water bath, flocculated and separated, to obtain supernatant and floc (c). The floc (c) is hydrolyzed, dried at 50-60 degrees C and pulverized, to obtain dry-finely floc (c1). The floc (c1) is pressed with sulfuric acid such that the solid-liquid ratio is 1 g:3-7 mL, to obtain hydrolyzate solution (d). Hydrolyzate solution (d) is added to hydrothermal reactor, hydrolyzed at 110-150 degrees C for 3.5-5.5 hours, processed with a base to neutral and filtered, to obtain residue (e). The residue (e) is washed with water until the filtrate which does not contain sulfate ion and dried, to obtain residue (e1). The residue (e1) is dried, and diosgenin is extracted using extraction agent, Soxhlet-extracted for 3-6 hours, cooled and crystallized, to obtain diosgenin.