A　novel　post-denitrification　system　fed　by　carbon　source　from　primary　sludge　(PS)　was　used　for　enhancing　biological　nitrogen　removal　(BNR)　of　low　C/N　wastewater.　This　system　included　one　anoxic/oxic　(AO)　reactor　and　a　special　reactor　for　simultaneous　sludge　fermentation　and　denitrification　(Sifeden).　Ammonia　was　nitrified　to　nitrate　in　AO　and　then　the　nitrate　was　reduced　to　dinitrogen　in　Sifeden,　into　which　PS　was　added　intermittently.　Results　showed　that　this　system　had　high　performance　on　nitrogen　removal.　Total　nitrogen　(TN)　removal　efficiency　was　higher　than　85%　and　the　effluent　TN　＜=　10mg/L　in　the　condition　of　influent　C/N　＜=　2.　In　Sifeden,　volatile　fatty　acid　(VFA)　produced　from　PS　fermentation　provided　electron　donor　for　nitrate　reduction,　and　PS　was　preliminarily　stabilized　simultaneously.　Oxidation-Reduction　Potential　(ORP)　had　a　significant　correlation　with　the　denitrification　performance.　TN　removal　efficiency　could　be　further　improved　if　adopting　proper　PS　addition　strategy　according　to　the　ORP　profiles.