In　biological　municipal　wastewater　treatment,　gene　level　analysis　of　community　structure　could　not　determine　functional　genes　that　actually　played　a　role　and　expression　of　viable　microorganism.　In　this　study,　reverse　transcriptional　PCR　(RT-PCR),　cDNA　high　throughput　sequencing　and　transcriptional　activity　analysis　were　conducted　to　investigate　active　microbial　community　with　nitrogen　and　phosphorus　removal　from　municipal　wastewater.　RT-PCR　and　correlation　heatmap　analysis　suggested　that　transcriptional　activities　of　bacteria　had　strong　correlation　with　performance　of　nitrogen　and　phosphorus　removal,　they　might　be　therefore　regarded　as　an　indicator　for　wastewater　treatment　monitoring.　When　DO　concentration　were　raised　from　0.6　mg/L　to　2　mg/L　and　C/N　ratio　from　3-4　to　5,　the　increase　of　population　abundance　and　transcriptional　activities　of　denitrifying　genes　improved　the　removal　efficiencies　of　COD　and　TN.　The　species　with　relatively　high　abundance　at　gene　level　were　not　really　active　species　at　transcription　level,　and　vice　versa.