Farmland soils in oil fields are liable to get polluted with petroleum hydrocarbons (PHs), which consequently leads to enrichment of some special PHs degrading microbial groups in the soils. In this study, soil samples were collected from typical farmland fields near five different oil wells in the Jianghan Oilfield located in Qianjiang City, Hubei Province for analysis of PHs degrading microbial groups, using bssA (benzylsuccinate synthase gene), a functional gene key to anaerobic benzenes degradation as biomarker, and community structure of the PHs degrading microbial groups was determined with T-RFLP (Terminal-restriction fragment length polymorphism) and clone library. On such a basis, environmental factors affecting community composition of the soil bssA were discussed. Results show that the content of polycyclic aromatic hydrocarbons (PAHs) in the soil varied in the range of 0.21~2.01 mg kg^-1, which indicates that the soil in this region was not seriously contaminated with PHs. Meanwhile, the T-RFLP analysis indicates that bssA diversity varied significantly from soil sample to soil sample in this oilfield, being the highest in the soil sample the highest in PAHs content, and its dominant group was in a fairly close kinship with sulfate-reducing bacterium or Geobacter. Furthermore, RDA (Redundancy analysis) reveals that the contents of soil available nitrogen, phosphorus and PAHs were all main factors affecting soil bssA diversity. To sum up, all the findings indicate that the bssA-bearing microbial groups in the soil of this oilfield are Beta -proteobacteria andDeta -proteobacteria, and in close kinships with Thauera, Azoarcus and Geobacter in phylogenesis. All these microbes might degrade PAHs through reducing metabolic processes of nitrate, sulfate, and iron.