The　application　of　partial　denitrification　coupling　with　anammox　(PD/A)　in　municipal　sewage　treatment　is　one　of　the　most　promising　research　field,　and　it　has　just　begun.　In　548　days　of　experiment　treating　real　domestic　sewage,　the　continuous　flow　reactor　was　started　up　by　adding　biocarriers　containing　anammox　bacteria　and　operated　stably　after　acclimatization.　The　PD/A　was　successfully　achieved　in　the　step-feed　AO　system.　Furthermore,　mass　balance　of　ammonium　revealed　that　anammox　could　contribute　32-47%　to　nitrogen　loss.　Compared　with　no　biocarriers　addition　phase,　the　nitrogen　removal　efficiency　(NRE)　increased　to　77.8　+/-　4.3%　and　the　effluent　total　inorganic　nitrogen　(TIN)　decreased　to　11.0　+/-　2.1　mg/L　at　the　COD/TIN　ratio　of　2.9　from　day　428　to　day　548　under　the　condition　of　anammox　biocarriers　addition　and　without　external　carbon　source.　Quantitative　polymerase　chain　reaction　(qPCR)　and　high-throughput　sequencing　analysis　showed　that　anammox　bacteria　on　the　biological　carrier　accounted　for　3.06%　of　the　total　bacteria　in　the　stable　phase,　which　was　much　higher　than　the　reported　＜0.003%　in　wastewater　treatment　plants　(WWTPs).　After　247　days　of　operation　with　anammox　biocarriers　addition,　the　abundance　of　anammox　bacteria　on　the　carriers　tended　to　be　stable　at　3.36　x　10(10)　gene　copies　g(-1)　dry　sludge.　The　activity　of　anammox　decreased　and　maintained　at　13.14　g　NH4+-N　m(3)　d(-1)　under　the　biocarriers-only　condition,　while　increased　from　11.71　g　NH4+-N　m(3)　d(-1)　to　25.65　g　NH4+-N　m(3)　d(-1)　in　the　hybrid　condition　of　biocarriers　and　flocs.　This　study　indicated　that　PD/A　is　effective　to　strengthen　nitrogen　removal　with　low　COD/TIN　ratio.