The　performance　of　immobilized　bacteria　by　waterborne　polyurethane　in　treating　steel　wastewater　with　nitrate　nitrogen　was　investigated.　It　found　that　the　optimal　C/N　ratio　was　5.0　using　glucose　as　an　electron　donor　and　the　hydraulic　retention　time　was　set　to　6　h　could　meet　the　needs　of　denitrification　in　this　study.　The　removal　efficiency　of　immobilized　denitrifying　bacteria　on　nitrate-nitrogen　in　steel　wastewater　reached　80%,　and　the　nitrate　concentration　in　the　effluent　was　less　than　5　mg/L,　indicating　that　microbial　immobilization　technology　has　a　better　treatment　effect　on　steel　wastewater.　High-throughput　sequencing　shows　that　steel　wastewater　has　a　domesticated　selection　effect　on　the　evolution　of　the　immobilized　bacteria,　making　the　bacteria　which　adapt　to　the　quality　of　the　steel　wastewater　to　be　dominant　bacteria.　Through　this　study,　we　believe　that　steel　wastewater　can　be　treated　in　a　targeted　manner　to　achieve　accurate　decontamination　by　microbial　immobilization　technology.