The　coexistence　of　nanoparticles　and　antibiotics　in　wastewater　treatment　plants　can　produce　combined　toxicity.　CuO　NPs　and　CIP　were　used　as　representative　substances　of　nanoparticles　and　antibiotics,　respectively,　to　investigate　the　long-term　coexistence　effects　of　CuO　NPs　and　CIP　on　the　operation　performance,　sludge　characteristics　and　microbial　community　in　aerobic　granular　sludge　(AGS)　systems.　The　nitrogen　removal　under　CuO　NPs　single　stress　slightly　improved.　Meanwhile,　the　carbon　and　phosphorus　removal　slightly　decreased　in　the　AGS　system.　CIP　single　stress　significantly　inhibited　the　removal　of　carbon,　nitrogen　and　phosphorus.　The　coexistence　stress　of　CuO　NPs　and　CIP　showed　an　obvious　synergistic　inhibition　on　the　removal　of　carbon,　nitrogen　and　phosphorus.　The　coexistence　stress　of　CuO　NPs　and　CIP　decreased　cell　membrane　integrity,　increased　lactate　dehydrogenase　(LDH)　release,　enhanced　extracellular　polymeric　substances　(EPS)　secretion,　and　significantly　changed　the　functional　groups　of　soluble　EPS(S-EPS)　in　AGS　systems.　The　coexistence　stress　of　CuO　NPs　and　CIP　changed　microbial　community　structure,　had　a　significant　synergistic　inhibition　on　biodiversity,　and　had　a　strong　toxicity　on　microorganisms.　©　2023　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.