A　novel　process　was　developed　for　real　domestic　wastewater　and　waste　activated　sludge　(WAS)　treatment　based　on　partial　denitrification,　anammox-biological　phosphorus　removal,　fermentation　and　partial　nitrification　(PDAPFPN).　After　246　days　of　operation,　the　effluent　concentrations　of　NH4+-N,　NO2--N　and　NO3--N　were　below　detection　limits　(0.1　mg/L),　and　the　effluent　concentration　of　PO43--P　was　0.1　mg/L　without　the　addition　of　external　carbon　source　in　PDA-PFPN　system.　Moreover,　the　sludge　reduction　efficiency　reached　48.1%　due　to　fermentation.　The　nitrite　accumulation　ratios　by　ammonia　oxidation　and　nitrate　reduction　pathway　were　60.6%　and　87%,　respectively.　Intracellular　metabolites　measured　by　liquid　chromatography　mass　spectrometer　(LC-MS/　MS)　suggested　that　different　intracellular　amino　acids　were　stored　and　consumed　at　different　duration,　and　intracellular　Valine,　Glycine　and　Lysine　were　not　utilized　in　oxic　stage.　Results　of　flow　cytometry　showed　that　the　proportion　of　intact　cells　decreased　from　94.7%　to　82.9%,　and　necrotic　cells　increased　from　5.3%　to　17.1%　with　the　increase　of　DNA　content　in　sludge　supernatant　and　cell　decay　rate,　indicating　the　occurrence　of　cell　death　and　lysis　and　leading　to　WAS　reduction.　Analysis　of　transcriptional　community　composition　revealed　that　partial　denitrification　bacteria　(Thauera),　anammox　bacteria　(Candidatus　Brocadia　and　Candidatus　Kuenenia),　simultaneous　phosphorus　removal　and　fermentation　bacteria　(Tetrasphaera)　and　partial　nitrification　bacteria　(Nitro-somonas)　coexisted　and　actually　worked　in　PDA-PFPN　system.　The　novel　PDA-PFPN　process　simultaneously　achieved　highly　efficient　nitrogen　and　phosphorus　removal　and　WAS　reduction　without　the　addition　of　external　carbon　source,　which　greatly　reduced　the　operation　cost　of　carbon　source　dosing　and　WAS　treatment　in　wastewater　treatment.