Partial-denitrification　(PD;　NO3??NO2?)　has　recently　been　proposed　to　be　a　feasible　choice　of　NO2?-N　supply　for　anammox　bacteria.　In　this　study,　an　aerobic/anoxic　process　for　treating　domestic　wastewater　was　operated　for　176　days　to　evaluate　the　feasibility　of　using　sludge　fermentation　liquid　for　partial　denitrification　of　the　wastewater.　Results　show　that,　with　the　ratio　of　C/N　(COD/　NO3?-N)　increased　at　anoxic　stage,　the　average　NO2?-N　concentration　in　the　effluent　and　nitrate-to-nitrite　transformation　ratio　(NTR)　at　anoxic　stage　showed　relative　growth.　High-throughput　sequencing　analysis　demonstrated　that　the　enhancement　of　PD　can　be　explained　by　the　increases　of　Thauera,　Paracoccus　and　Enterobacteriaceae.　Moreover,　Candidatus_Brocadia　(0.13%)　was　detected　as　the　predominant　anammox　bacteria.　Ex-situ　isotopic　tracing　technique　analysis　assessed　that　the　ratio　of　anammox　role　(ra%)　was　7.29%.　This　study　has　a　great　potential　for　being　coupled　with　the　anammox　bacteria　for　advanced　nitrogen　removal.