The　application　of　anaerobic　ammonium　oxidizing　(anammox)　in　the　treatment　of　municipal　wastewater　with　low　matrix　has　always　been　challenging.　At　the　same　time,　the　substitution　of　seawater　and　the　extensive　use　of　deicing　salt　in　winter　increase　the　salinity　of　municipal　wastewater　with　low　matrix,　which　increases　the　difficulty　of　treatment.　This　study　focused　on　the　performance　of　anammox　biofilm　(AM)　and　granular　sludge　(AG)　in　salinity　environment　from　the　point　of　view　of　signal　molecular　regulation　and　sludge　structure　cohesion.　AM　could　adapt　and　form　a　stable　biofilm　after　acclimation　at　0.6　%　salinity,　while　AG　collapsed　due　to　the　decrease　of　particle　size　and　the　sharp　decrease　of　the　abundance　of　anammox　bacteria.　AM　protected　anammox-related　genus　such　as　Candidatus　Kuenenia　and　Ignavibacterium　by　releasing　more　endogenous　C8-HSL　and　C12-HSL　to　ensure　stable　nitrogen　removal.　Endogenous　C8-HSL　and　C12-HSL　stabilize　the　anammox　process　by　enhancing　EPS　to　increase　water　output　and　increasing　COD　consumption　by　some　heterotrophic　bacteria,　respectively.　The　modularization　of　the　microbial　community　network　of　AM　was　0.937.　the　rich　microbial　diversity　improves　the　salinity　impact　performance　of　AM.　The　microorganisms　responsible　for　nitrogen　metabolism,　sulfur　metabolism,　and　protein　export　in　AM　were　significantly　higher　than　AG　when　the　salinity　reached　0.6　%.　In　conclusion,　this　research　illustrated　that　the　AM　could　maintain　good　nitrogen　removal　performance　in　the　mainstream　municipal　low-salt　wastewater,　clarified　the　mechanism　of　signal　molecules　regulating　and　promoting　the　anammox　process,　and　provided　theoretical　support　for　the　application　of　anammox　in　mainstream　engineering.