Abstract: Based on the optimization of colorimetric conditions with Folin-Ciocalteau method and single-factor tests, a central composite design was used to investigate the effects of three factors just as ultrasonic power, liquid-solid ration and extraction temperature on the yield of polyphenols from Brassica campestris L.stem barks.A predictability mathematical model was constructed and the optimum extraction parameters for the extraction of polyphenols were determined using response surface analysis (RSA) .The optimum extraction was as follows:ultrasonic power was 249W, liquid-solid ration was 52∶1 (mL∶g) , extraction time was 34min.The validation test result under this condition was 5.84mg/g and achieved 97.34% of the theoretical prediction value.Process conditions for extraction polyphenols from Brassica campestris L.had the characteristics of stable and reliable, high yield and non-polluting etc.and could be used to guide the polyphenols extraction from Brassica campestris L.waste.