Abstract: In the present study， isoflavone was extracted from Pueraria lobata（Willd.） Ohwi root tuber collected in Tujia Mountain by ultrasoundassisted ethanol extraction. Based on single factor test analysis， main technology parameters of the extraction process were optimized by response surface design of 4 factors and 4 levels， and antioxidant effects of the extracted isoflavone were also studied. The results showed that the optimum extraction technology was as follows: the ethanol concentration was 810%，ultrasoundassisted extraction time was 41.2 min， extraction temperature was 61.2 ℃， solid to liquid ratio （m/V） was 1∶9.5， and particle size of raw material was 40 mesh. Under this condition， the extraction rate of isoflavone reached 3.43%. The antioxidant effects of the extracted isoflavone were weaker than that of vitamin C， but it could yield synergetic effect with vitamin C.

Key words: Pueraria lobata（Willd.） Ohwi, isoflavone, antioxidants