The nitrilon wastewater was pretreated with aerobic activated sludge, suspended carrier expanded bed and anaerobic biological reactor. The results showed that the aerobic activated sludge was unfit for treating nitrilon wastewater due to its CN - toxicity and high concentration of difficult degraded organic matter. With the increase of operational time, the activity of sludge lost gradually and a lot of microbe died. The effect of suspended carrier expanded bed treating nitrilon wastewater was worse and the removal efficiency of contaminated matter was under 15%. The anaerobic biological reactor was good at treating nitrilon wastewater and the removal efficiency of contaminated matter was up to 35%. Meanwhile the wastewater quality was improved and the biochemical performance of nitrilon wastewater was enhanced, which were beneficial for advanced treatment to nitrilon wastewater by sequential biological treating processes.