The　start-up　of　anaerobic　ammonia　oxidation　(ANAMMOX)　processes　at　low　temperatures　is　quite　difficult.　In　this　study,　the　fast　start-up　(43　days)　of　ANAMMOX　biofilm　processes　at　18　+/-　3　degrees　C　was　achieved　by　adding　enhanced　ANAMMOX　granules　(LT-granules)　into　the　inoculated　denitrification　sludge.　The　results　showed　that　the　addition　of　LT-granules　significantly　reduced　the　duration　of　the　three　start-up　phases　(cell　lysis　phase,　activity　lag　phase,　and　activity　elevation　phase)　of　reactor　R-2　compared　with　the　control　group　R-1　without　LT-granules.　It　was　demonstrated　that　LT-granules　released　high　contents　of　N-hexanoyl-DL-homoserine　lactone　(C6-HSL),　N-octanoyl-DL-homoserine　lactone　(C8-HSL),　and　N-3-oxohexanoyl-L-homoserine　lactone　(3OC6-HSL).　The　C6-HSL　and　C8-HSL　from　LT-granules　were　strongly　positively　correlated　with　the　concentrations　of　polysaccharides　(TB-PS)　and　proteins　(TB-PN)　in　tightly　bound　extracellular　polymeric　substances　(TB-EPS)　in　R-2　biofilms,　respectively.　Thus,　LT-granules　promoted　the　release　of　TB-PS　and　TB-PN　from　the　biofilm　in　R-2　during　activity　lag　and　activity　elevation　phases,　improving　the　biofilm　adhesion　performance.　Furthermore,　it　was　proved　that　the　C6-HSL,　C8-HSL,　and　3OC6-HSL　from　LT-granules　significantly　stimulated　the　relative　abundance　of　Candidatus　Brocadia　genus　and　the　expression　of　functional　genes　hzo　and　hzsA　in　R-2　biofilms　during　activity　lag　and　activity　elevation　phases.　These　are　the　main　reasons　why　adding　LT-granules　promoted　the　start-up　of　reactor　R-2　at　18　+/-　3　degrees　C　effectively.　This　study　is　the　first　work　to　accelerate　the　start-up　of　the　ANAMMOX　biofilm　system　at　the　low　temperature　by　the　economical　quorum　sensing　(QS)　regulation　based　on　endogenous　N-acyl-homoserine　lactone　signals　(AHLs)　and　supply　a　new　way　for　the　rapid　start-up　of　ANAMMOX　processes　in　the　low-temperature　environment.