Abstract: The treatment of printing and dyeing wastewater is a problem of great difficulty and a focus of public attention because of its high color intensity， variation of water quality and poor biodeg? radation. The wastewaters were treated by immobilized microorganism technology. The experimental results showed that the average removal efficiencies of COD and color were over 90% and 70%，respectively，under the conditions of pH = 7，influent concentration = 300 mg/L and hydraulic retention time（HRT）= 16 h.

Key words: immobilized microorganism technology, printing and dyeing wastewater, COD, color, removal efficiency