Abstract: The craft of corn-bract flavonoid extraction with ultrasonic and its content measurement with colorimetry was conducted and the best distillation conditions found to be at 700W of ultrasonic power,extraction temperature of 60℃，material proportion of 50g/mL,ethanol concentration of 60%,extraction time of 35 min.The highest total flavonoid rate gets 1.225%.Antioxidative test results show good performance of flavonoid scavenging capacity in both superoxide radical systems and hydroxyl radical systems.Free radical scavenging capacity, IC₅₀ flavonoids, to superoxide radical system and hydroxyl radical are respectively 1.5μg/mL and 0.14mg/mL and stronger than vitamin C(V_C).In DPPH system,IC₅₀ flavonoid is 0.2mg/mL and IC₅₀ V_C is 0.075mg/mL.However,within selected dosage,the highest scavenging capacity of flavonoids outweighs that of V_C.The tests show the suitability of flavonoid as good natural radical scavenger.