Polyamide　(PA),　a　prevalent　microplastics　(MPs),　is　often　collected　from　wastewater　treatment　plants.　However,　the　responses　of　partial　nitrification　system　to　PA　MPs　are　unclear.　The　short-term　and　long-term　effect　of　PA　MPs　on　the　partial　nitrification　system　was　slight,　but　the　ammonia　oxidation　rate　decreased　slowly　with　the　increase　of　PA　MPs　concentration.　Meantime,　the　PA　MPs　addition　could　decrease　the　microbial　diversity,　alter　microbial　community　structure　of　the　system　and　facilitate　the　propagation　of　antibiotic　resistance　genes　(ARGs)　including　fabI,　intI1　and　Tn916/1545.　Correlation　analysis　and　network　analysis　indicated　that　Ferruginibacter,　Hyphomicrobium,　Terrimonas,　Brevundimonas　and　Plasticicumulans　in　the　system　might　be　the　dominant　hosts　of　ARGs.　In　addition,　oligotyping　analysis　indicated　not　all　oligotypes　of　the　relevant　genus　showed　positive　correlation　with　ARGs.　In　general,　PA　MPs　had　almost　no　effect　on　performance　but　altered　community　structure　and　increased　ARGs　spread　risk　of　the　partial　nitrification　system.