Eight kinds of facultative anaerobes using petroleum hydroc-arbon as sole carbon source are screened out from hundreds of oil-bearing waste water samples based on physical and ch-emical condition of Daqing oil field. Systematic biochemical property evaluation and core-flooding experiment show that the eight kinds of facultative anaerobes can grow and repro-duce on crude oil under anerobic condition. They also can de-grade crude oil and decrease its viscosity, produce active substance and reduce the interfacial tension (IFT) between fermented solution and crude oil. Chromatographical analysis shows that the light component of oil which has treated with bacteria increases by 30%, ΣC21-/ΣC22+ increases by 54%.The oil movability got better. Pr /nC17 and Ph/nC18 increases by 55% and 57% respectively. The PH value of the fermented solution reduces from 7 to 5. The acid content in the fermented solution increases from 17.57mg/L to 948.83mg/L. The IFT between fermented solution and crude oil reduces form 35.67mN/m to 8.10mN/m. The viscosity of crude oil decreases from 28.1mPa·s to 18.06mPa·s. The oil recovery by the microbial flooding is about 10%OOIP over that of the water flooding. How the microbes displace the residual oil was directly observed by an electronic microscope during a microscopic core flooding experiment.

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