Abstract: Oil radish seed was used as research object，ethanol as the solvent，the total flavonoids in oil radish seed were extracted by ultrasonic assisted method，and content of total flavonoids was determined by ultraviolet spectrophotometry.On the basis of single factor experiment，response surface method was used to optimize extraction conditions.Through analysis of four factors of material liquid ratio，ethanol concentration，ultrasonic temperature and ultrasonic time，and the influence of two factors on content of total flavonoids，it was concluded that the most influential factor was ultrasonic temperature，followed by ultrasonic time，then material liquid ratio，and finally ethanol concentration.When the material liquid ratio was 1∶25，ethanol concentration was 70%，ultrasonic temperature was 53 ℃，ultrasonic time was 28 min，the extraction rate was the highest，and the total flavone content was 15.18 mg/g.It was close to predicted value of 15.15 mg/g，which indicated that the process was reliable and has certain reference value.