This　study　focused　on　the　nitrogen　(N)　and　phosphorus　(P)　removal　performance　optimization　in　simultaneous　nitrification-endogenous　denitrification　and　phosphorus　removal　(SNEDPR)　systems.　An　anaerobic　(180min)/aerobic　sequencing　batch　reactor　(SBR)　fed　with　domestic　wastewater　was　studied　for　optimization　of　N　and　P　removal　performance　of　SNEDPR　by　regulating　the　aerobic　dissolved　oxygen　(DO)　concentration　(0.3~1.0mg/L)　and　aerobic　duration　time　(150~240min).　FISH　technology　was　also　employed　to　analyze　the　population　dynamics　of　functional　microorganisms　in　the　SNEDPR　system.　Results　indicated　that　the　effluent　PO43--P　concentration　was　below　0.4mg/L,　effluent　TN　concentration　decreased　from　14.3mg/L　to　8.7mg/L,　and　TN　removal　efficiency　increased　from　75%　to　84%　with　aerobic　DO　concentration　decreased　from　1.0mg/L　to　0.3mg/L　and　aerobic　duration　time　increased　from　150min　to　240min.　SNED　was　enhanced　by　the　decreased　aerobic　DO　concentration,　with　SNED　efficiency　increased　from　34.7%　to　63.8%.　The　enhanced　SNED　reduced　the　effluent　NO3--N　concentration,　improved　the　N　removal　performance,　and　strengthened　the　intracellular　carbon　storage　at　the　following　anaerobic　stage.　FISH　results　showed　that　the　populations　of　PAOs,　GAO　and　AOB　(ammonia　oxidizing　bacteria)　still　maintained　at　high　levels　in　the　127-day　optimized　SNEDPR-SBR　(accounting　for　29%±3%,　20%±3%　and　13%±3%　of　total　biomass,　respectively),　which　ensured　the　P　uptake,　nitrification　and　denitrification;　however,　NOB　(nitrite　oxidizing　bacteria)　reduced　by　50%,　which　provided　a　possibility　to　achieve　N　removal　through　simultaneous　partial　nitrification-endogenous　denitrification　in　the　SNEDPR.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.