Abstract: This study aimed to explore the optimal ultrasonic wave-assisted extraction of total flavonoids in passion fruit and evaluate its stability and antioxidant activity. Based on the results of single factor experiments,extraction process was optimized by response surface methodology. The stability of total flavonoids was studied by investigating the influence of temperature and light on the absorbance of the flavonoid extract. And the antioxidant activity of total flavonoids was assessed by scavenging assays of ·OH,NO₂^- and total antioxidant power. The optimal extraction conditions were obtained as follows:Ethanol concentration 61%,liquid-material ratio 59:1 mL/g,temperature 56℃,ultrasonic power 240 W,ultrasonic time 25 min. Under the optimal conditions,an average extraction rate of 2.19%±0.03% was obtained,which was similar to the expect yield 2.21% of the regression model. The total flavonoids in passion fruit peel was stable blew 60℃ under dark. High temperature and ultraviolet light had a destructive effect on it. Investigation on antioxidant activity showed that the clearance rates on ·OH,NO₂^- were 81%,43% when the flavonoid concentration was 30 μg/mL and total antioxidant power was 0.687,which would be stronger with higher concentration. Based on the above research results,the optimal extraction conditions are stable and feasible,and the total flavonoids should be kept at low temperature and protected from light to keep its strong antioxidant activity.