Abstract: ObjectiveThe technology condition of ultrasonic-assisted extraction of flavonoids from Guangxi big fruit hawthorn leaves was optimized in order to provide technical reference for the resource utilization of Guangxi big fruit haw-thorn leaves.MethodThe ultrasonic-assisted extraction of flavonoids from hawthorn leaves was optimized by using sin-gle factor and response surface test,taking the Guangxi big fruit hawthorn leaves as the raw material,and ultra-pure wa-ter as the extractant. The effects of four factors including ultrasonic power,extraction temperature,extraction time and solid liquid ratio on extraction rate of flavonoids were studied.ResultAccording to response surface test,the quadratic regression model equation was established:Y=52.91+1.41A+1.08B+1.63C+0.51AB+0.89AC+0.052BC-4.53A2-0.97B2-1.36C2(Y referred to the extraction rate of flavonoids;A referred to extraction temperature;B referred to extraction time;and C referred to solid liquid ratio). The optimum technology conditions for ultrasonic-assisted extraction of flavonoids from big fruit hawthorn leaves were as follows:the ultrasonic power was 140 W;the extraction temperature 59℃;extrac-tion time 120 min and solid liquid ratio 1:56(g/mL). Under such conditions,the extraction rate of flavonoid was 54.18 mg/g and the error was small compared with the predictive value(53.86 mg/g). According to importance order,the influ-ence of the three factors on the extraction rate of flavonoids from Guangxi big fruit hawthorn leaves was solid liquid ratio>extraction temperature>extraction time. And the interaction between extraction temperature and solid-liquid ratio had sig-nificant influence on the extraction rate of flavonoids from hawthorn leaves(P<0.05).ConclusionThe ultrasonic-assisted water extraction optimized by response surface has following advantages:high extraction rate,high precision and stable technology,so it can be used for the promotion and application in production.