The　aim　of　this　study　was　to　investigate　the　denitrification　performance　and　analyze　the　variation　of　microbial　communities　in　immobilized　particles　which　used　in　real　municipal　wastewater　treatment.　The　bioreactor　has　achieved　good　denitrification　effect　on　real　municipal　wastewater　treatment,　the　NO3--N　and　TN　removal　efficiencies　reached　77.4%　and　68.3%,　respectively.　High-throughput　sequencing　shows　that　the　community　structure　and　relative　abundance　of　bacteria　changed　greatly,　especially　at　the　phyla　and　genes　levels　in　immobilized　particles.　Through　the　investigation　of　this　paper,　we　think　the　influence　of　microflora　variation　should　be　considered　when　using　microbial　immobilized　technology　for　wastewater　treatment,　and　we　suggest　that　immobilized　particles　cannot　be　used　indefinitely　and　it　needs　to　be　replaced　periodically.