The anoxic-aerobic process was used to treat n-phenylglycinonitrile wastewater from a chemical plant. Furthermore, the chemical process was used to remove ammonia from effluent of bio-chemical process. The results show that when the influent contains COD Cr 1 000-2 000 mg/L and NH 3-N 300 mg/L, the effluent would contain COD Cr 200-300 mg/L and NH 3-N 30 mg/L. The treated water can be reused as cooling water for the factory.