Abstract:The method of ultrasonic assisted extraction was used to extract flavonoids from honeysuckle and ginkgo leaves. The two kinds of flavonoids extraction was mixed according to certain proportion. Then the mix－ ture on vitro antioxidant activity of oxidation resistance was analysed by testing scavenging ability of DPPH radi－ cal. The results showed that the two kinds of flavonoids from honeysuckle and ginkgo leaves had obvious removal effects on DPPH free radicals， and the half of clearance （IC50） were 58.14 μg/mL and 61.32 μg/mL. And Isobologram analysis demonstrated the response of factor of flavonoids from honeysuckle and ginkgo leaves were both located in the left of the addition line and 95 % confidence interval. There was a significant difference be－ tween experimental IC50mix and theoretical IC50add. The interaction index （γ） were all less than 1， the mixture ex－ hibited stronger removing capacity of DPPH radicals that the single one. When the proportion of honeysuckle flavonoids and ginkgo flavonoids（all of the following compound ratio refered to the mass ratio） was 1 ∶ 9， γ was 0.71. The collaborative interaction effect of removing DPPH free radicals was the best.