An abundance of SRB, TGB and IB corrosive bacteria were generally detected in the produced water of shale gas fields with hydraulic fracture throughout the production cycle. CO₂ fracturing technology is one of the most promising technologies for shale oil development. To date, limited research has been directed to the corrosive bacteria and the diversity of microbial communities in the produced water for the shale oil field. With the maximum possible number method (MPN) and high-throughput sequencing method, the change of the concentrations for SRB, TGB, and IB bacteria with the production time and the bacterial community characteristics in the produced water of shale oil field was investigated. The results showed that high concentrations of 10³ ~ 10⁷ cells/mL for SRB, TGB, and IB bacteria were measured in the river water to make fracturing liquid, fracturing liquid, and the produced water within 1 day of production. However, a significant decrease in the concentration of SRB, TGB, and IB bacteria was observed after 47 days of production. The sensitivity of SRB, TGB, and IB to the injected CO₂ during fracturing was different. The growth of SRB, TGB was inhibited while the growth of IB was promoted by CO₂.99.9% of SRB, TGB and IB were killed when the produced water was exposed to 150 ℃,2 MPa for 10 h. The bacteria in the produce water within 1 day of production were mainly made up of the exogenous bacteria introduced during the fracturing process, which made less impact on the microbial community with the extension of production time. The diversity of bacteria significantly increased with the increase of production time. Shannon index was 2.4 and 2 for the produced water after 0.67 day and 1 day of production, and it increased to 7.7 and 7.4 after 47 and 76 days of production. The bacterial community structure underwent significant changes with production time. The microbial community was dominated by Proteobacteria that represented approximately 20% to 97% of the total cell number for fracturing liquid, and the produced water within 76 days of production. A high relative abundance of Firmicutes, Acidobacteria, Actinomycetes, Bacteroidetes, and Chloroflexi was detected in the produced water after 47 and 76 days of production. Potential petroleum degrading bacteria was measured in the produced water of shale oil wells, such as Bacilli, Pseudomonas, Psychrobacter and Marinobacterium.