In　this　research,　a　new　system　that　combination　of　the　ion　exchangemembrane　and　ultrafiltration　membrane　(IEM-UF)　nitrogen　enrichment　with　shortcut　nitrification　and　denitrification　was　proposed　for　low　carbon　nitrogen　ratio　of　domestic　sewage.　The　performance　of　nitrogen　and　COD　removalin　the　system　were　studiedunder　the　three　stage　operating　condition.　Meanwhile,　the　characteristicsof　the　microbial　community　in　the　system　were　analyzed　by　high　throughput　technology,　andthe　effect　of　the　flora　changes　on　the　nitrogen　removal　was　investigated.　The　rate　of　nitrite　accumulation　in　the　shortcut　nitrification　reactor　reached　above　90%only　19d　when　C/N　was　3and　DO=0.5mg/L.When　the　ratio　of　denitrifying　influent　was　2:　1,　the　average　removal　rates　of　COD　and　NOx--Nreached　above　80%　and　89%,　respectively.　The　maximum　removal　rate　of　TN　was　above　64.8%.　Besides,　the　change　of　bacterial　community　structure　in　the　three　stage　was　consistent　with　the　change　of　nitrogen　removal　efficiency.　Under　the　three　operatingconditions,　the　proportion　of　Nitrosomonas　accounted　for　the　proportion　of　the　genus　in　the　shortcut　nitrification　reactor　was　about　3.69%,　5.48%　and0.53%　respectively.　As　well　asthe　sum　of　denitrifying　bacteria　Dechloromonas　and　Thauerain　the　denitrification　reactor　accounted　for　33.35%,　25.62%　and　20.52%,　respectivelyunder　the　three　stage.　©　2018,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.