Abstract: Dyeing wastewater was treated with a two-stage system of hydrolysis acidification and food chain reactor (FCR). The influences of hydraulic retention time (HRT) on the removal efficiency of COD, chromaticity, NH3-N and anilin were examined, and the mechanism and efficiency of nitrogen removal at the optimum HRT were discussed. When HRT was 30 h, the average removal ratios of COD, chromaticity, TN, NH₃-N and anilin were 93.3%, 81.9%, 79.9%, 98.1% and 74.8%, respectively. The effluent average concentrations of COD, chromaticity, TN, NH₃-N and anilin all met the first level of China Textile and Dyeing Industry Water Pollutants Discharge Standard (GB 4287—92). It is shown that this system, which not only removes both color and organic matter effectively, but also has great removal effect on nitrogen, can be used in treating high-and middle-concentration dyeing wastewater.