Abstract: In order to realize the intensive management and resource utilization of coking wastewater, improve the treatment efficiency of biochemical system, and reduce the operation cost, the Beiying coking plant of Bensteel takes the opportunity of upgrading and reforming the wastewater treatment system of three production areas under its jurisdiction as the turning point, the process of“Pretreatment + enhanced pretreatment + A/A/O biochemical treatment + biological fluidized bed + ozone catalytic oxidation + membrane treatment (ultrafiltration + reverse Osmosis) + concentrated water treatment” was adopted in series, and the operation mode of zero dilution and zero emission was adopted, combined with the problems existing in the operation of the traditional A-A-O process, the pretreatment system, the biochemical system and the post-mixing system were optimized and improved respectively, for other units in the same industry to provide valuable reference experience.