Complete　ammonia　oxidation　(comammox)　bacteria　have　been　detected　in　full-scale　wastewater　treatment　plants.　However,　the　slow　growth　rate　limits　the　research　and　applications　of　comammox.　Quorum　sensing　(QS)　is　an　intercellular　communication　process　to　regulate　microbial　physiological　metabolism,　but　its　role　in　comammox　Nitrospira　has　rarely　been　reported.　In　this　study,　denitrifying　filter　backwash,　return　and　anoxic　tank　sludges　were　utilized　as　seeding　inoculums　to　enrich　comammox　bacteria,　with　the　addition　of　three　types　of　signaling　molecules　(C6-HSL,　C8-HSL　and　C12-HSL).　Under　ammonia-　and　dissolved　oxygen　(DO)-limited　conditions,　12　lab-scale　sequencing　batch　reactors　(SBRs)　were　operated　for　90　days.　Quantitative　polymerase　chain　reaction　(qPCR)　and　16S　rRNA　gene　sequencing　supported　the　enrichment　of　comammox　Nitrospira　in　all　SBRs.　The　highest　absolute　abundance　of　comammox　Nitrospira　amoA　gene　was　detected　in　the　anoxic　tank　sludge　with　exogenously　added　C8-HSL,　reaching　an　average　of　2.34x106　copies/(g　sludge).　In　this　condition,　comammox　Nitrospira　and　ammonia-oxidizing　archaea　contributed　up　to　94　%　of　the　total　nitrification　activity,　with　ammonia-oxidizing　bacteria　accounting　for　only　6　%.　Overall,　the　role　of　QS　in　comammox　Nitrospira　enrichment　was　confirmed,　with　signaling　molecules　significantly　accelerating　the　growth　of　comammox　Nitrospira,　promoting　functional　enzyme　activity,　and　strengthening　nitrifying　bacterial　competitiveness.　Among　the　signaling　molecules　tested,　C8-HSL　exhibited　the　most　pronounced　promotional　effect,　followed　by　C6-HSL　and　C12-HSL.　Using　anoxic　tank　sludge　as　the　seed　sludge　with　the　addition　of　C8-HSL　provides　a　rapid　and　reliable　enrichment　strategy　for　comammox　Nitrospira.　These　findings　offer　insights　into　the　role　of　QS　in　comammox　bacteria　enrichment,　and　might　facilitate　the　development　of　biotechnologies　for　wastewater　treatment　based　on　comammox　Nitrospira.