Abstract: The soluble(sPPO)and membrane bound(mPPO)polyphenol oxidase were extracted from potato by citric acid combined phosphate buffer solution and ultrasound assisted combined Tris-HCl buffer extraction method,respectively,and the enzyme specific activity was used as the evaluation index. The extraction process of sPPO and mPPO were optimized by response surface method on the basis of single factor experiments. The results showed that the optimal extraction process of sPPO were as fllows:The solid-liquid ratio was 1:3.2,the extraction time was 12 h,and the buffer pH was 7.1,the specific activity of sPPO was(130.5±2.4) U/mg under this condition. The influence of three factors on sPPO extraction were as follows:Extraction time>solid-liquid ratio>buffer pH. The optimal extraction process of mPPO were as fllows:The material-liquid ratio was 1:5.2,the extraction time was 7 h,and the buffer pH was 6.7,the specific activity of mPPO was(686.4±7.9) U/mg under these condition. The influence of three factors on mPPO extraction were as follows:Ultrasonic time>solid-liquid ratio>buffer pH. The extraction conditions of sPPO and mPPO could be predicted and analyzed by the response surface model.