Abstract: In this study, the ultrasonic-assisted extraction technology conditions of coumarin from cortex fraxini were optimized by orthogonal experiment on the basis of single factors tests using cortex fraxini as the raw material and coumarin extraction yield as the indicator. Results showed that the optimal extraction conditions were determined as follows: surfactant addition of 3%, ethanol volume fraction of 50%, extraction temperature of 60 ℃, extraction time of 40 min, and solid-liquid ratio of 1 ∶10（g/mL）. Under these conditions, the extraction yield of coumarin reached to 1.038%. Subsequently, the antioxidant activity determination results showed that the scavenging capacities of cortex fraxini extract on DPPH and hydroxyl free radicals were both higher than that of VC under the same concentrations, which indicated that the coumarin in cortex fraxini had strong antioxidant activity.