In order to understand the change of the microbial community during process of MEOR displacing in Baolige oil field， the type and abundance of the microbial community in the key oil wells was analyzed by high-throughput sequencing technology. The results showed that the microbial diversity of the analyzed reservoir was rich，while the species distribution was very uneven.The abundant genera were Pseudomonas，Acinetobacter，Alishewanella，Thauera，Halomonas and Wolinella during the process of microbial enhanced oil recovery，which indicated that the main microbial role in this stage was to produce biosurfactant and degrade the hydrocarbon. The biosurfactant concentration increased by 44.23% on average，and the surface tension of the produced liquid decreased by 12.75% on average. When the injection of the nutrients to the reservoir was over，the concentration of hydrocarbon degrading bacteria decreased，and the abundance of anaerobacteria and methanogens increased. The methanogens abundance increased from 0.116% to 40.77% in oil well B18-41. In this stage，the main microbial role was to produce gas by anaerobic fermentation. After the completion of microbial displacement of 60 days，the methane gas content increased 10.65%.