Hydrolysis-acidification + aerobic biological processes were conducted experimentally to treat oilfield wastewater pretreated with physical and chemical treatment in Xinjiang oilfield. The results showed that when the COD concentration in influent was 190-220 mg x L(-1), that in effluent reduced to 65-75 mg x L(-1) under HRT of 10h in both hydrolysis-acidification process and aerobic biological process, reaching the strictest requirement of Effluent Standards for Wastewater from Petroleum Development Industry (GB3550-83). Using GC/MS technology, the relative content of various organic pollutants was analyzed to discover the transfer and degradation law in the oilfield wastewater in biological treatment process. The system of DNA extraction technique, PCR and DGGE reacting systems were practical to analyze the microbial community in the hydrolysis-acidification and aerobic biological processes. The predominant sequences of several 16S rDNA DGGE fragments were determined and confirmed in comparison in GeneBank (NCBI).