Abstract: The ultrasonic- assisted extraction conditions of polyphenol from michelia alba leaves were optimized by response surface methodology.Based on single factor test,a 4- factor,3- level Box- Behnken experimental was adopted including dependent variables( ethanol concentration,liquid to material ratio,ultrasonic time and ultrasonic temperature) and independent variable( yield of polyphenols). The results showed that the optimum conditions were ethanol concentration 54%,liquid to material ratio 19 m L / g,ultrasonic time 25 min,ultrasonic temperature66 ℃. The yield of total flavonoids could be up to 9.94% under the optimal extraction condition,the relative error was 0.30% compared to the predictive value,which indicated the feasible model fitted well with the experimental data.The research could be developed a theoretical foundation and a scientific basis for the extraction of total flavonoids from michelia alba leaves into natural antioxidant.