A　lab-scale　anoxic/oxic　(A/O)　system　was　used　to　reveal　the　key　active　triclosan-degrading　bacteria　(TCS-DB)　in　this　study.　The　results　showed　that　TCS　was　mainly　removed　by　metabolism　of　heterotrophic　bacteria　(accounting　for　about　62%),　and　the　potential　metabolic　pathway　was　the　break　of　ether　bond　in　TCS　formed　2,4-dichlorophenol,　and　further　dechlorination　formed　phenol　or　other　metabolic　end　products.　DNA-based　stable　isotope　probing　(DNA-SIP)　assay　further　revealed　that　Methylobacillus　accounting　for　20.75%　in　C-13　sample　was　the　key　active　TCS-DB.　Furthermore,　methylotrophy　and　methanol　oxidation　were　found　to　be　the　potential　metabolic　routes　of　TCS　degradation　by　functional　annotation　of　prokaryotic　taxa　analysis.　Interestingly,　TCS　accelerated　the　propagation　of　antibiotic　resistance　genes　(fabI)　and　inti1　which　positively　correlated　with　several　functional　microorganisms　(p　＜　0.05).　This　study　contributes　to　comprehend　the　potential　mechanism,　metabolic　pathway　and　microbial　ecology　of　TCS　biodegradation　in　A/O　system.