Coking wastewater,usuallyladen byrefractory organic contaminants is often treated by aerobic biological processes.Despite of several studies onphylogenetic diversity of microbialcommunities,little is understood about theirfunctional genediversity and metabolic potential in coking wastewater treatment system.Herein,a comprehensive functional gene array,Geochip 5.0 was used to examine functional genes and metabolic potential of microbial communities in a long run(~500 days)bench-scale aerobic bioreactor treating coking wastewater.Results revealed that a large number(67396)of diverse functional genes involved in almost all microbial bioprocess categories targeted by Geochip 5.0 including carbon cycling(mainly,carbon compound degradation),nitrogen and sulfur cycling,organic pollutant removaletc were consistently observed across all examined sludge samplesduring treatment.The abundance of several functional genes related to degradation of organic pollutants,mainlyaromatic ring cleavage hydroxylase/dioxygenase and nitrilasewere significantly(Mantel test,P<0.05)correlated with influent nitrogen and effluent ammonia.Additionally,nitrogen cycle ammonification genes(gdh,ureC)also showed significant correlation with influent nitrogen and effluent ammonia.pH demonstrated significant correlation on microbial functional structure related to all major bioprocesses indicating that pH might play important role in shaping microbial diversity.Variance partitioning analysis revealed pHcould explain nearly 14.8%variation of microbial functional structure of the treatment system.This study provides insights into the microbial functional ecology of high strength coking wastewater treatment and revealed possible microbial transformation of organic pollutants.