Abstract: Aiming at the issues in microbial flooding process of Baolige oilfield, the following points were deeply studied in this paper indoor physical simulation experiments, the effect of different flooding ways on enhance oil recovery, the relationship between output bacterial concentration and injected bacteria concentration and influence of nutrient solution concentration on maintaining the produced fluid concentration of bacteria. The results showed that the microbial flooding by injecting 1% bacterial fluid plus 1% nutrient solution can enhance 16.77% oil recovery. And the produced fluid can further enhance oil recovery by 5.74% when supplemented nutrient solution bacterial fluid and ferment about 10-12h before keep on microbial continuous flooding, and the produced fluid bacteria concentration can reach 108 cells / mL or more. However, due to the adsorption of cell core on microbial and the core permeability effect on microbial migration, the concentration of produced bacteria fluids was always one order of magnitude lower than the concentration of injected bacteria fluids. Using the produced fluids reinjection added above 0.25% nutrient solution, the concentration of produced bacteria fluids can be maintained at 107 cells/mL or more. The results can provide technical support for on-site inject program design.