Maintaining　the　efficient　performance　of　anaerobic　ammonia　oxidation　(ANAMMOX)　biofilm　under　low-temperature　conditions　is　a　great　challenge.　The　effects　of　two　exogenous　signaling　molecules,　hexanoyl　homoserine　lactone　(C6-HSL)　and　octanoyl　homoserine　lactone　(C8-HSL),　on　the　ANAMMOX　biofilm　process　were　examined　under　the　natural　temperature　in　winter.　The　results　showed　that　the　addition　of　C6-HSL　and　C8-HSL　promoted　the　nitrogen　removal　performance　of　the　process　under　low　temperature　fluctuation,　which　increased　the　total　nitrogen　removal　by　48.09%　and　44.36%,　respectively,　and　effectively　enhanced　the　adaptability　of　ANAMMOX　biofilm　to　the　low-temperature　environment.　Under　the　low-temperature　fluctuation,　C6-HSL　and　C8-HSL　regulated　the　activities　of　hydrazine　dehydrogenase　(HDH)　(1.77and　1.57times　higher　than　that　of　the　control　group,　respectively),　which　significantly　enhanced　the　activities　of　ANAMMOX;　promoted　the　secretion　of　PN　and　PS　in　the　extracellular　polymers　(EPS),　especially　in　the　TB-EPS,　and　altered　the　hydrophobicity　of　the　secondary　structure　of　proteins,　which　led　to　enhanced　biofilm　adhesion　performance　(The　OD600values　were　enhanced　by　55.12%　and　68.32%,　respectively).　In　addition,　based　on　16S　rRNA　sequencing,　C6-HSL　and　C8-HSL　effectively　promoted　the　growth　of　Candidatus　Kuenenia　at　low　temperature　and　up-regulated　the　abundance　of　functional　genes　related　to　nitrogen　metabolism.　©　2024　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.