The optimal pH, stability, tissue distribution and activity of polyphenol oxidase (PPO) from Litopenaeus vanname were studied. The effects of different packages (vacuum and non-vacuum package) and different storage temperatures (-18 ℃, 4 ℃, 25 ℃) on the melanosis and PPO activity of Litopenaeus vanname were analyzed. Meanwhile, the relationship of melanosis with PPO catalytic reaction rate and storage temperature and the relationship between PPO activity and storage temperature were discussed. The results showed that the activity of PPO from the shell and head of Litopenaeus vanname was higher, while it was lower in the abdomen muscle and pleopods. The optimal pH of PPO was 6.0 and it was more stable with higher activity at pH 6.0~8.0. The melanosis was positively correlated with storage temperature and catalytic reaction rate of PPO; the relative activity of PPO was negatively related to storage temperature; vacuum package effectively isolated Litopenaeus vanname from oxygen and lower temperature inhibited PPO activity, thus PPO catalytic reaction rate was decreased and the melanosis was prevented. It will provide a theoretical reference for controlling the melanosis of Litopenaeus vannamei during storage and processing.