The　partial　nitrification-anammox　(PN/A)　process　is　a　promising　method　for　the　treatment　of　municipal　wastewater.　It　is　necessary　to　clarify　the　responses　of　PN/A　system　to　antimicrobial　agent　triclosan　(TCS)　widely　existed　in　the　influent　of　wastewater　treatment　plants.　In　this　study,　it　was　found　that　PN/A　system　was　robust　to　cope　with　0.5　mg/L　TCS.　Specifically,　the　control　reactor　reached　80%　total　nitrogen　removal　efficiency　(TNRE)　on　day　107,　while　the　reactor　feeding　with　0.5　mg/L　TCS　reached　the　same　TNRE　on　day　84.　The　results　of　the　activity　test,　high-throughput　sequencing　and　DNA-based　stable　isotope　probing　showed　that　0.5　mg/L　TCS　did　not　impede　the　performance　of　ammonia　oxidizing　archaea,　ammonia　oxidizing　bacteria　(Nitrosomonas)　and　anammox　bacteria　(Candidatus　Brocadia　and　Ca.　Kuenenia),　but　significant　inhibited　the　nitrite　oxidizing　bacteria　(Nitrospira　and　Ca.　Nitrotoga)　and　denitrifying　bacteria.　The　influent　TCS　led　to　the　increase　of　EPS　content　and　enrichment　of　four　resistance　genes　(RGs)　(intI1,　sul1,　mexB,　and　tnpA),　which　might　be　two　principal　mechanisms　by　which　PN/A　can　resist　TCS.　In　addition,　functional　bacteria　carrying　multiple　RGs　also　contributed　to　the　maintenance　of　PN/A　system　function.　These　findings　improved　the　understandings　of　antimicrobial　effects　on　the　PN/A　system.