Abstract: In order to study the extraction processes and the antioxidant activity of seabuckthorn flavonoids,the seabuckthorn fruit from a new variety named as Zhonghua Changbai Mountain No.27 cultivated for 17 years was selected for subsequent analysis.On the basis of single factor experiment,ratio of material and liquid,extraction times,ethanol concentration and temperature were investigated.The optimal extraction conditions were optimized by the response surface method,and the optimal extraction conditions of seabuckthorn flavonoids were as follows:ethanol concentration 90%,extraction 3 times,solid-liquid ratio 1:60(g/mL),extraction temperature 80℃.Under the optimal extraction conditions,the extraction rate of flavonoids was 2.665%.In vitro,antioxidant capacity was determined by DPPH free radical scavenging,hydroxyl free radical scavenging,and determination of reducing ability under the optimal extraction conditions,and the results of anti-oxidative activity indicated that IC₅₀of scavenging hydroxyl free radical by sea buckthorn flavonoids (0.001 mg/mL~0.005 mg/mL) was 0.001 5 mg/mL,whereas the IC₅₀of Vc was 0.005 6 mg/mL.These phenomena demonstrated that hydroxyl radical scavenging capacity of seabuckthorn flavonoids was stronger than that of Vc.At the same time,the IC₅₀of total reducing power of seabuckthorn flavonoids and Vc was 0.197 0 mg/mL and 0.083 9 mg/mL;the IC₅₀of DPPH scavenging activity of seabuckthorn flavonoids and Vc was 0.089 7 mg/mL and 0.031 3 mg/mL.These results indicated that the total reducing power and hydroxyl radical scavenging capacity of flavonoids was less than that of Vc.The results also showed that the antioxidant activity increased as the concentration increased.Our research confirmed that sea buckthorn flavonoids have antioxidant effect,which provides theoretical basis for the comprehensive development and utilization of seabuckthorn new varieties and related basic researches.