Abstract: The enzymatic characteristics of polyphenol oxidase (PPO) from Pleurotus eryngii Quel.was studied by spectrophotometer at 420nm.The results showed that the optimum substrate for this enzyme was catechol.The PPO enzyme had the highest activity at pH6.0 and 35℃.The enzyme activity would been inactivated completely after exposure to 90℃for 2min.The kinetics of enzyme-catalyzed reaction of PPO was in accord with Michaelis-Menten equation, with K_m and V_max values of 0.0207mol/L and 41.32U/min, respectively.Seven kinds of metal ions had different effects on PPO activity, Al～ (3+) and Mn～ (2+) had an inhibitory effect on the enzyme, while Fe～ (3+) had a stimulative effect on the enzyme, and the effect of Mg～ (2+) , Zn～ (2+) , Ca～ (2+) and Cu～ (2+) on enzyme was not obvious.In the range designated, it was increasing in inhibitory effects of ascorbic acid, citric acid, NaHSO₃ and L-Cysteine against enzyme activity with the increasing concentration, and the order as follow:ascorbic acid﹥NaHSO₃﹥L-cysteine﹥citric acid.