Produced water, the significant wastewater in association with oil and gas production in oilfield, is characterised by the presence of crude oil and also many inorganic substances. It is very difficult to treat this water to meet the reinjection water quality for low and ultra-low permeability reservoirs. In the present paper, the treatment of produced water from Daqing Oilfield was investigated using a submerged membrane bioreactor (SMBR). The SMBR was operated for about 6 months with constant permeate flux and hydraulic retention time HRT of 12 hours. The experimental results showed that the SMBR had a high retention of crude oil, total suspension substance (TSS), turbidity, ammonia nitrogen (NH4+-N), and medium grain size. In the permeate, the content of crude oil, NH4+-N and turbidity were respectively lower than 1 mg/L, 1mg/L, and 1 NTU, while the TSS content was below detection limits (2.5 mg/L) and medium grain size was undetectable. The pemeate could reach the grade A1 criteria specified in the Recommendation Standard and Analysis Method for the Clastic Rock Reservoir Injection Water Quality (SY/T 5329-94, China).