Abstract: The research aimed to determine the optimal ultrasonic- assisted extraction process of Helwingia japonica helwpolyphenols and its antioxidant activity in vitro. On the basis of design and analysis of single- factor experiments,through which the optimal ultrasonic power and the frequency of extraction were found to be 65 W and two times,the technological conditions of ultrasonic- assisted for the Helwingia japonica polyphenols were optimized by response surface methodology and the antioxidant activity of Helwingia japonica polyphenols was also studied by DPPH· and ABTS⁺·.The result showed that the optimum extraction conditions of Helwingia japonica polyphenols were the volume fraction of 40.8% ethanol,ultrasonic time 4.8 min,solid- liquid ratio 1 ∶ 60( g∶ m L),extraction temperature 67.5 ℃.Under this condition,the yield of polyphenols obtained was 29.43 mg /g.The tests of antioxidant capacity showed that Helwingia japonica polyphenols had strong deoxidizing ability,and the IC₅₀ of DPPH· and ABTS⁺·were 44.28 mg /L and 35.07 mg /L respectively.Therefore,Helwingia japonica has a good potential as a natural antioxidant used in food or medicine industries.