The　nitrogen　removal　characteristics,　physicochemical　properties,　and　microbial　community　composition　of　four　different　anaerobic　ammonium　oxidation　(anammox)　sludge　morphologies　were　investigated.　The　morphologies　considered　in　this　study,　namely　suspended　sludge　(Rs),　biofilm　(Rm),　granular　sludge　(Rg),　and　encapsulated　biomass　(Re),　were　prepared　from　floc　sludge.　The　results　show　that　Re　exhibited　the　maximum　anammox　activity,　followed　by　Rg,　Rm,　and　Rs.　Additionally,　the　anammox　contribution　rate　was　higher　in　Rg　and　Re.　The　higher　extracellular　polymer　content　in　Rg　promoted　sludge　accumulation,　and　tryptophan　was　observed　in　Rm　and　Rg,　which　was　replaced　by　humic　acids　in　Rs.　Re　showed　the　largest　specific　surface　area,　hydrophobicity　and　strength,　and　its　good　structure　ensured　enrichment　of　anammox　bacteria　(AnAOB).　In　terms　of　the　microbial　community,　the　functional　bacterium　Candidatus　Kuenenia　accounted　for　the　highest　proportion　in　Rm　(39.27%),　but　the　presence　of　both　anaerobic　and　aerobic　regions　led　to　increased　community　complexity　with　more　nitrifying　bacteria.　In　contrast,　Rg　and　Re　had　a　more　specific　microbial　community.　In　addition,　denitrifying　bacteria　tended　to　grow　in　Rs,　while　nitrifying　bacteria　were　retained　in　Rm.　The　AnAOB　were　more　likely　to　be　enriched　in　sludge　aggregates　(both　Rm　and　Rg)　and　carriers　(Re).　Through　correlation　analysis,　the　potential　relationship　involving　bacterial　flora　evolution　of　each　sample　was　clarified.　Finally,　the　structural　models　of　different　morphologies　of　sludge　were　proposed.　This　study　deepens　the　understanding　of　various　anammox　sludge　morphologies　as　well　as　provides　useful　information　for　the　cultivation　of　AnAOB　and　further　application　of　anammox.