The oil recovery is increased using the indigenous microorganism flooding through specific indigenous microorgan-isms by injecting nutrients. The microbial community structure and the dynamic changes of the dominant bacterium in the pro-duction liquid of microbial flooding in Zhan3 block of Shengli Oilfield were analyzed, through which the relationship between the biological features and the dynamic changes of production performance was studied. It is found that there exits clear correla-tion between microbial diversity, dominant bacteria content and the oil production performance. A significant negative correla-tion is observed between the microbial diversity and the oil production. And the oil production is affected directly by the alter-native synergism of 4 dominant bacteria. It is also found that a significant positive correlation exists between the content of dom-inant bacteria and oil production. And the change of oil production lags behind the change of the biological features.