As　more　and　more　microplastics　(MPs)　and　triclosan　(TCS),　which　are　added　in　consumer　products,　enter　wastewater　treatment　plants　with　sewage,　there　are　concerns　about　the　impacts　of　the　co-occurrence　of　MPs　and　TCS　on　biological　wastewater　treatment.　In　this　study,　the　co-effects　of　four　1　mg/L　MPs　(polyethylene　(PE),　polystyrene　(PS),　polyvinyl　chloride　(PVC)　and　polyamide　(PA))　and　0.5　mg/L　TCS　on　nitrification　were　investigated　in　lab-scale　nitrifying　sequencing　batch　reactors　(SBRs)　(SBR-PE,　SBR-PS,　SBR-PVC　and　SBR-PA)　relative　to　control　which　received　no　MPs　(SBR-CK).　The　removal　rates　of　NH4+-N　and　TCS　in　SBR-CK　were　around　100%　and　92%,　respectively.　Compared　with　SBR-CK,　no　measurable　inhibition　was　observed　on　nitrification　in　SBR-PE　and　SBR-PS,　however,　SBR-PVC　and　SBR-PA　rapidly　lost　nitrification　function　during　14　days,　which　might　be　due　to　the　reducing　of　MLSS　caused　by　PVC,　PA　and　TCS　co-loading.　Furthermore,　PS,　PVC　and　PA　decreased　the　removal　of　TCS.　The　co-occurrence　of　TCS　and　PS,　PVC,　PA　increased　extracellular　polymeric　substances,　reduced　microbial　diversity　and　shifted　microbial　communities.　Notably,　the　acrA-03,　mexF,　fabI,　intI1,　intI3　and　IS613　genes　were　enriched　by　MPs　and　TCS　co-loading.　Therefore,　the　removal　of　MPs　and　TCS　from　wastewater　should　be　prioritized.