The　endogenous　partial　denitrification　process　(EPD)　led　by　glycogen-accumulating　organisms　(GAOs)　has　become　an　alternative　to　NO2-　supply　in　mainstream　anaerobic-ammonia　oxidation　(anammox).　However,　low　autotrophic　nitrogen　removal　contribution　is　an　urgent　problem　that　needs　to　be　solved　in　simultaneous　endogenous　partial　denitrification/anammox　(EPDA)　system.　This　study　used　anaerobic　duration　optimization　to　enhance　the　autotrophic　nitrogen　removal　capacity　of　EPDA　system.　The　results　showed　that　the　EPDA　activity　increased　from　0.67　to　1.09　mg　N/g　VSS　center　dot　h　after　anaerobic　time　was　extended　to　120　min.　This　significantly　improved　the　contribution　of　anammox　to　TIN　removal,　increasing　from　23.5　%　to　61.6　%.　During　the　phase　III,　Eff.TIN　of　4.5+1.8　mg/L　and　NRE　of　92.2　%+3.0　%.　The　enrichment　of　AnAOB　(Candidatus　Brocadia)　and　GAOs　(Defluviicoccus)　was　responsible　for　maintaining　the　stability　of　the　EPDA　process.　This　study　provides　a　feasible　optimization　strategy　for　improving　the　contribution　of　autotrophic　nitrogen　removal　in　the　EPDA　system.