A submerged membrane bioreactor (MBR) was employed to treat wastewater containing different content of seawater in this work. During the process, the operating conditions were as follows: COD was 800-1000 mg/L, ammonium-N was 80-100 mg/L, pH was 7.5-8.5, mixed liquor suspended solids (MLSS) was around 7000 mg/L, dissolved oxygen (DO) was 2-4 mg/L. The results showed that the ammonium-N removal was better than COD removal. Sludge settling property was good in saline wastewater treatment, and the sludge became quite compact as the wastewater contained 70% seawater. Membrane fouling was aggravated mainly because the extracellular polymeric substances (EPS). The trans-membrane pressure (TMP) increased from 5 kPa to 44 kPa during first 180 days of operation. After the physical and chemical cleaning, it dropped to 8 kPa. The filtration capacity of the membrane was recovered.