The extraction of total flavonoids from buckwheat hust was optimized by ultrasound-assisted ethanol extraction method. Through the optimization by single factor, with extraction efficiency of total flavonoids, the effects of ultrasonic extraction time, ultrasonic extraction temperature, ethanol concentration and material-to-liquid ratio of total flavonoids from buckwheat hust were investigated. Through the optimization by response surface method, the optimal extraction conditions were found. The experimental results showed that the best conditions were ethanol concentration 69%, material-to-liquid ratio 1∶51(m∶V), extraction time 30 minute and ultrasonic extraction temperature 59 ℃, the yield rate of total flavonoids was 3.542%.