Biological　nitrogen　removal　of　wastewater　with　low　COD/N　ratio　could　be　enhanced　by　the　addition　of　wasted　sludge　fermentation　liquid　(SFL),　but　the　performance　is　usually　limited　by　the　introducing　ammonium.　In　this　study,　the　process　of　using　SFL　was　successfully　improved　by　involving　anammox　process.　Real　municipal　wastewater　with　a　low　C/N　ratio　of　2.8-3.4　was　treated　in　a　sequencing　batch　reactor　(SBR).　The　SBR　was　operated　under　anaerobic-aerobic-anoxic　(AOA)　mode　and　excess　SFL　was　added　into　the　anoxic　phase.　Stable　short-cut　nitrification　was　achieved　after　46d　and　then　anammox　sludge　was　inoculated.　In　the　stable　period,　effluent　total　inorganic　nitrogen　(TIN)　was　less　than　4.3　mg/L　with　removal　efficiency　of　92.3%.　Further　analysis　suggests　that　anammox　bacteria,　mainly　affiliated　withCandidatus_Kuenenia,　successfully　reduced　the　external　ammonia　from　the　SFL　and　contributed　approximately　28%-43%　to　TIN　removal.　Overall,　this　study　suggests　anammox　could　be　combined　with　SFL　addition,　resulting　in　a　stable　enhanced　nitrogen　biological　removal.　(c)　Higher　Education　Press　2020