Denitrification of Coke oven waste water is most biological.That COD/NH 3 N is too high is adverse to biological denitrification.Iron scrap method is used to pretreat coke oven wastewater in order to degrade COD.Coke oven wastewater is pretreated by iron scrap with ancillary material. A good result is got that the removal efficiency of COD cr of wastewater is 40% or so without regulating pH of wastewater and the solution is alkaline.The results show that the factors arragned in important order as the follows:the quantity of iron scrap,graphite,ancillary material A, treatment time,aeration time.The removal efficiency of COD does not lower ater the reactor has run about two months. The results are stable.