Two　EGSB　(expanded　granular　sludge　bed)　reactors　(R0　and　R1)　with　2　g-VSS　L-1　anammox　sludge　were　established　to　intensify　specific　anammox　activity　(SAA)　and　biomass　growth　under　limited　inoculum,　and　in　response　to　a　hydraulic　strategy.　During　the　start-up　period,　HRT　(hydraulic　retention　time)　was　set　at　12h　in　R0,　while　sharply　decreased　from　12h　to　4h　in　R1.　The　sludge　characteristics,　abundance,　and　community　shifts　were　also　investigated　to　explore　their　correlations　with　SAA　enhancement.　The　results　showed　that　after　120　days,　SAA　of　R1　finally　reached　1.6　kg-N　kg-VSS-1　per　day,　which　was　1.8-　times　that　of　R0.　The　initial　shortened　HRT　in　R1　changed　the　assembly　mode　of　granulation,　and　unlike　the　flocculant　sludge　in　R0,　the　formation　and　growth　of　small　granules　played　a　more　critical　role　in　improving　SAA　in　R1.　Also,　the　tightly　bound　layer　of　extracellular　polymeric　substances　promoted　a　rapid　increase　in　the　proportion　of　particles　larger　than　0.6　mm　in　size,　which　significantly　enhanced　SAA.　QPCR　showed　the　corresponding　abundance　of　anammox　bacteria　was　gradually　saturated　to　5.72E+10　copies　g-SS-1　when　the　SAA　tended　to　be　stable.　While　the　increase　in　＂saturated　abundance＂　particles　(＞1.0　mm)　speeded　up　the　proliferation　of　anammox　bacteria.　The　corresponding　doubling　time　was　shortened　from　36.8-10.0　d　in　R1,　which　made　up　for　the　disadvantage　of　the　initial　biomass　loss.　The　high-throughput　analysis　revealed　Candidatus　Kuenenia　stuttgartiensis　was　the　dominant　genus　(34.22　%)　in　R1.