As　a　common　surfactant,　quaternary　ammonium　compounds　(QACs)　are　often　used　as　the　main　ingredient　in　disinfection　products.　Hence,　the　three　most　commonly　used　QACs　were　selected　for　this　study,　including　alkyltrimethylammonium　compounds　(ATMACs),　alkylbenzyldimethylammonium　compounds　(BACs)　and　dialkyldimethylammonium　compounds　(DADMACs).　Typical　QACs　at　low　(0.2　mg/L),　medium　(1　mg/L)　and　high　(5　mg/L)　concentrations　to　the　enhanced　biological　phosphorus　removal　(EBPR)　systems　were　studied.　The　QACs　exposure　study　was　conducted　for　a　total　of　93　days　using　four　sequential　batch　reactors.　DADMAC-C12　had　the　greatest　inhibitory　effect　on　EBPR　performance,　followed　by　BAC-C12　and　ATMAC-C12.　On　day　51,　R1　(stimulated　by　ATMAC-C12)　and　R2　(stimulated　by　BAC-C12)　recovered　their　EBPR　performance,　whereas　the　P　removal　efficiency　of　R3　(stimulated　by　DADMAC-C12)　was　still　only　65.9　%.　Furthermore,　the　dosage　of　both　ATMAC-C12　and　BAC-C12　promoted　sludge　granulation,　whereas　DADMAC-C12　caused　slight　breakdown　of　formed　aerobic　granular　sludge.　The　median　volumetric　diameter　in　R3　initially　increased　to　a　maximum　of　409.9　mu　m　and　finally　decreased　to　352.6　mu　m　at　the　end　of　the　operation.　The　stress　of　QACs　resulted　in　an　enrichment　of　pathogenic　bacteria　(e.g.,　Flavobacterium)　and　antibiotic　resistant　bacteria　(e.g.,　Pseudomonas)　in　the　systems.　The　abundance　of　Pseudomonas　in　R1　and　R3　finally　reached　up　to　9.40　%　and　9.44　%,　respectively.　Additionally,　QACs　disrupted　bacterial　cell　membranes　and　resulted　in　the　release　of　intracellular　resistent　genes　in　sludge　(si-RGs).　Then,　si-RGs　converted　to　extracellular　RGs　in　sludge　and　RGs　in　water.　Zoogloea,　Rhizobium,　Turneriella　and　Aquimonas　were　the　dominant　potential　hosts　of　RGs　in　EBPR　systems　dosed　with　QACs.　This　study　can　serve　as　an　important　reference　for　the　control　of　RGs　in　EBPR　processes.