Insights　into　the　microbial　communities　in　municipal　wastewater　treatment　plants　(WWTPs)　are　critical　for　the　optimization　of　biological　nutrient　removal　process.　However,　our　understanding　about　the　spatiotemporal　characteristics　of　the　microbial　communities　in　WWTPs　remains　limited.　In　the　present　study,　264　samples　were　collected　biweekly　from　four　spatially　independent　corridors　in　a　typical　municipal　WWTP.　The　annual　compositional　and　metagenomic　characteristics　were　investigated　based　on　multiple　ecological　indicators　using　statistical　tests.　The　results　revealed　that　the　microbial　community　compositions　from　the　four　corridors　showed　significantly　high　similarities,　as　revealed　by　the　statistical　analysis　at　the　operational　taxonomic　unit　(OTU)　level.　Consistent　with　the　OTU　level　results,　the　functionality　of　the　microbial　communities　in　the　four　independent　corridors　also　showed　significant　similarity.　In　comparison,　the　dynamics　of　the　microbial　community　over　the　year　showed　two　successional　peaks　of　the　microbial　communities　with　the　spatial　similarity,　and　this　resulted　in　three　alternative　stable　states　of　the　microbial　communities　in　a　calendar　year.　The　microbial　communities　only　drifted　in　July　and　November,　suggesting　an　uneven　community　succession　pattern　driven　by　seasonal　variation　in　environmental　conditions.　The　functional　characteristics　were　found　to　be　relatively　conservative　compared　to　the　microbial　community　succession,　which　revealed　the　decoupling　between　the　composition　and　functionality　of　the　microbial　community　in　the　municipal　WWTP.　The　present　study　provides　an　in-depth　overview　of　the　microbial　communities　in　a　municipal　WWTP　and　will　be　useful　for　the　establishment　of　the　connection　between　ecological　characteristics　and　the　operational　stability　of　WWTPs.