Abstract: It was necessary to study the composition of total cyanide to improve the cyanide removing ability of coking wastewater treatment plants. Composition and removal characteristics of total cyanide were investigated. Results showed that iron-cyanide complexes accounted for more than 90% of total cyanide in the bio-treated coking wastewater, and iron-cyanide complexes were removed by microorganism through adsorption more than degradation in the dark biological reactor, even if which could decompose very fast under the illumination. In addition, low pH and high pE condition with polymeric flocculant had the positive effect for the chemical precipitation.