Without　additional　carbon　sources,　a　low　endogenous　denitrification　rate　(EDNR)　is　the　critical　factor　limiting　its　application　in　postdenitrification　systems.　This　study　optimized　the　quantitative　distribution　of　anaerobic　carbon　source　removal　pathways　based　on　chemometrics　for　the　first　time　and　explored　the　effect　of　anaerobic　carbon　conversion　on　anoxic　endogenous　denitrification.　Results　showed　that　enhancing　the　intracellular　carbon　storage　of　glycogen　accumulating　organisms　(GAOs)　by　optimizing　anaerobic　duration　can　effectively　improve　the　EDNR.　The　anaerobic　stage　was　proposed　to　end　at　the　peak　concentration　of　polyhydroxyalkanoates　(PHAs).　A　two-stage　endogenous　denitrification　system　was　established　to　explore　the　long-term　operating　performance　before　and　after　optimizing　anaerobic　duration.　Results　showed　that　the　average　NO3-　removal　rate　increased　by　25%.　qPCR　and　optimized　stoichiometric　analyses　indicated　that　the　relative　abundance　and　intracellular　carbon　storage　proportion　of　GAOs　increased　by　67%　and　25%,　respectively.　This　study　provided　an　effective　strategy　to　improve　postdenitrification　efficiency.