Abstract: Enzymatic browning is formed easily in sweet potato processing. In this paper, the characteristics of Polyphenol Oxidase (PPO) from sweet potato and its control methods were studied by spectrophotometry. The results indicated that the activity and browning intensity of PPO from sweet potato peel was two times than those of internal tissue, and sweet potato had a lower PPO activity at pH 4.5. During sweet potato starch processing, the addition of 0.01%～0.05% citric acid or 0.005%～0.01% ascorbic acid or 0.05%～0.1% sodium sulfite, all combining with peeling sweet potato, would markedly inhibit the enzymatic browning caused by PPO, and improve the quality of starch.