To optimize the ultrasonic extraction auxiliary ionic liquids extraction process for flavonoids from Lotus Leaf and to evaluate the anti-oxidant activity. With ionic liquid concentration，ultrasonic power and ultrasonic time as influencing factors，flavonoids yield as an evaluation index，the extraction process was optimized by response surface method on the basis of single factor test．Subsequently the scavenging effects of flavonoids on DPPH，·OH free radicals were determined．The optimal conditions were determined to be 0.9 mol·L-1 of 1-hexyl-3-methylimidazole tetrafluoroborate([C6mim]BF4）as extraction solvent, 1:25 g·mL-1 for solid- liquid ratio 0.9 mol·L-1 for ionic liquid concentration，186W for ultrasonic power，and 24min for ultrasonic time，and 70℃ for extraction temperature ,total flavonoids demonstrated the extraction rate of 4.65%. When the mass concentration was 1.6 mg·mL-1，the scavenging rates of DPPH and ·OH radical were 63.2% and 55.4%，and the corresponding half inhibitory concentration (IC50) was 1.512 mg·mL-1and 2.140 mg·mL-1，the absorbance of reducing power determination was 0.72Abs. This stable and reliable method can be used for the extraction for flavonoids with significant in vitro antioxidant activity from Lotus Leaf.