Abstract: OBJECTIVE To investigate the ultrasonic-assisted extract on total flavonoids from Salvia miltiorrhiza Bge. and evaluate its in vitro antioxidant activity. METHODS On the basis of single-factor test, the ultrasonic-assisted extraction process parameters of total flavonoids from Salvia miltiorrhiza Bge. were optimized by the response surface method on the methanol concentration(A), extraction time(B) and extraction temperature(C). Meanwhile, the scavenging effects of total flavonoids from Salvia miltiorrhiza Bge. on superoxide free radical(O₂^-·), hydroxyl free radical(·OH) and DPPH· were determined. RESULTS The optimum conditions for total flavonoids of Salvia miltiorrhiza Bge. were as follows:methanol concentration was 71%, ultrasonic time was 52 min, and extraction temperature was 55℃. Under these conditions, the yield of total flavonoids could reach 12.493%. The total flavonoids had a certain scavenging effect on O₂^-·, ·OH and DPPH·, with the maximum scavenging rate of 93.4%, 60.3% and 40.3%, respectively. CONCLUSION The Box-Behnken design and response surface analysis can well optimize the ultrasonic-assisted extraction of total flavonoids from Salvia miltiorrhiza Bge. and has good predictability. The total flavonoids from Salvia miltiorrhiza Bge. have antioxidant activity in vitro, so this plant is worth further research and utilization.