Abstract: The ultrasonic-assisted extraction of total flavonoids from Sterculia lanceolata and antioxidant activity were studied. The influences of the ratio of Sterculia lanceolata to solvent,ethanol concentration,extraction power,extraction time and extraction temperature were investigated by single factor experiment,and the extraction process were optimized by orthogonal test with total flavonoids yield as index. The results showed that the optimal of extraction were as follows:the ratio of sterculia lanceolata to solvent was 1:25 (g/mL),ethanol concentration was 60%,extraction power was 60 W,the extraction was token place at 70℃ for 65 min. Under these conditions,the yield of total flavonoids was 2.36%±0.0002%. Antioxidant test showed that the hydroxyl radical scavenging activity increased with the increasing concentration of total flavonoids from the leaves of sterculia lanceolata. At the concentration of 4.92 mg/mL,the total flavonoids exhibited a maximum hydroxyl radical scavenging rate of 73.58%.