The　characteristics　and　mechanism　of　hollow　anammox　granular　sludge　with　different　settling　property　were　investigated　through　the　analysis　of　morphology,　structure　and　microbial　community.　According　to　settling　property,　the　granules　from　an　anammox　continuous　stirred-tank　reactor　were　classified　into　settling　granules　(SG)　benign　floating　granules　(BFG)　and　malignant　floating　granules　(MFG).　As　the　settling　performance　deteriorated,　the　extracellular　polymeric　substances　(EPS)　content　of　the　granules　increased.　The　microstructure　showed　that　the　number　of　pores　changed　significantly　for　SG,　BFG,　and　MFG.　Transfer　distance　increased　with　increasing　particle　size.　The　analysis　of　EPS　and　rheological　properties　indicated　that　EPS　is　a　key　driving　force　of　floating　and　proliferation　in　the　lifecycle　of　hollow　anammox　granule.　The　results　of　microbial　community　revealed　that　EPS-hydrolyzing　bacteria　were　biological　factors　that　weaken　structure　strength　of　granule.　©　2022　Elsevier　Ltd