Nitrite　oxidizing　bacteria　(NOB)　was　cultured　mixedly　in　whether　nitrification　sludge　or　partial　nitrification　sludge　system,　as　a　result,　its　characteristics　are　not　so　clear　to　the　researchers.　In　this　paper,　NOB,　which　was　inoculated　by　the　excess　activated　sludge　from　the　pilot-scale　SBR　in　the　same　lab,　was　enriched　with　the　way　of　increasing　NO2--N　concentration　gradually,　and　combining　high　concentration　of　Free　nitrite　acid　(FNA)　and　DO.　After　65days,　FISH　analysis　showed　that　more　than　80%　of　the　bacteria　population　was　NOB　(Nitrobacter:　80%;　Nitrospira:　5%),　which　demonstrated　the　successful　enrichment　of　NOB.　Furthermore,　the　activated　sludge　granulated　naturally　under　the　average　MLSS　concentration,　MLVSS/MLSS　and　SVI　of　700　mg/L,　0.278　and　6　mL/g,　respectively.　The　reason　about　the　extremely　low　SVI　was　probably　that　the　sludge　had　high　fraction　of　inorganics,　which　could　be　used　as　crystal　nucleus　to　form　the　granules.　Results　of　the　research　indicated　that　even　with　the　wastewater　whose　NO2--N　concentration　was　up　to　1000mg/L,　this　sludge　could　play　a　good　performance　with　specific　nitrifying　rate　and　specific　OUR　of　131.03　mg/(g　MLVSS·h)　and　169.5　mg　O2/(g　MLVSS·h),　respectively.