The present study evaluated the efficiency of ultrasonic and fermented pretreatment technology for diosgenin production from Diosorea zingiberensis C.H. Wright (DZW). The optimum extraction conditions were as follows: ultrasonic pretreatment condition, 20 min, 50 kHz, 100W; fermented pretreatment condition, 30 degrees C, 3d and 0.8g yeast dosages per 100 g raw materials; acidic hydrolysis condition, 1.5 mol/L sulfuric acid, 4 h; petrol extraction condition, 5 h. Under these conditions, diosgenin yield could reach 2.30%. Scanning electron micrographs indicated morphology changes of materials during diosgenin extraction process. UV-vis and GC-MS analysis revealed wastewater from the new approach contained 20 kinds of organic compounds which were mainly acids, esters, ketones and hydrocarbons. The research indicated the new approach could not only increase 42.5% diosgenin yield, recover 81.6% starch and 50.8% cellulose, but also efficiently reduce 69.7% COD, comparing with the conventional approach. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.