Abstract: Camellia sinensis var.assamica green tea of Fengqing in Yunnan province was selected as raw material and conducted post- fermentation process of pu- erh tea to study the most appropriate pH, temperature and reaction substrate as well as the variations of PPO activity, enzyme protein contents and specific activity during the process. The result showed that the PPO had the maximum activity at pH5.5, 55℃ and EGC was the natural substrate.The PPO activity and specific activity presented the wavy ascension tendency.The PPO activity was more active than the beginning of fermentation. Enzyme protein content descended generally, but the trend was not obvious.