Activated　sludge　contains　highly　complex　microbial　communities,　which　play　crucial　roles　in　pollutant　removal　performance　in　wastewater　treatment　plants　(WWTPs).　Metagenomic　sequencing　was　applied　to　characterize　microbial　community　and　functional　profiles　within　activated　sludge　from　a　full-scale　municipal　WWTP　carrying　out　simultaneous　nitrogen　and　phosphorous　removal　(SNPR).　We　applied　the　assembled　contigs　(N90　of　591　bp)　and　predicted　genes　to　conduct　taxonomic　and　function　annotations,　respectively.　Results　revealed　the　extraordinary　microbial　diversity　of　activated　sludge,　which　included　detection　of　minority　populations　that　are　difficult　to　be　explored　by　traditional　molecular　methods.　Taxonomic　analysis　indicated　that　the　dominant　bacterial　phyla　were　Proteobacteria,　Nitrospirae,　Bacteroidetes,　Actinobacteria　and　Firmicutes.　The　abundance　of　the　key　organisms　involved　in　nitrogen　and　phosphorous　removal　were　qualified.　Aerobic　ammonia-oxidizing　bacteria　distinctly　dominate　over　ammonia-oxidizing　archaea　and　anaerobic　ammonium　oxidation　bacteria.　Various　key　enzymes　involved　in　the　global　nitrogen　cycle　were　annotated　in　the　activated　sludge.　High　abundance　of　the　known　polyphosphate　accumulating　organisms　was　detected　(approximately　4.89%　of　the　overall　population　reads),　supporting　good　phosphorous　removal　performance.　This　study　provides　a　comprehensive　insight　into　the　community　structure　and　diversity　of　the　SNPR　system,　and　will　provide　foundation　for　optimal　operation　of　nutrient　removal　systems.