Granular　sludge　has　been　believed　to　be　a　promising　technology　in　wastewater　biological　treatment.　However,　the　formation　of　granules　at　low　substrate　concentration　is　a　difficult　task　that　has　seldom　been　achieved.　This　study　aimed　at　forming　the　granules　in　the　recently　developed　partial-denitrification　(PD,　NO3--N　-＞　NO2--N)　for　nitrite　production.　Two　sequencing　batch　reactors　(SBRs)　were　operated　at　a　low　nitrate　of　30　mg　N/L　with　nitrate　loading　rate　(NLR)　of　0.12　(R1)　and　0.24　kg　N/m(3)/d　(R2).　Results　showed　that　the　granulation　of　PD　sludge　experienced　a　developing　and　matured　process　with　the　progressive　increase　in　size　followed　by　maintaining　a　stable　value.　Higher　NLR　resulted　in　a　more　rapid　granulation　with　the　larger　and　looser　structure.　While　the　granules　under　lower　NLR　appeared　to　be　denser　and　more　compact　with　better　settling　ability.　Microbial　communities　of　two　SBRs　were　revealed　to　show　little　difference,　with　the　PD　functional　bacteria　of　Thauera　(50.7%　in　R1　and　55.4%　in　R2)　dominated　during　the　granulation　process.　The　Flavobacterium,　likely　to　be　closely　related　with　sludge　granulation,　accounted　for　a　higher　proportion　in　R2　(10.16%)　than　R1　(5.91%),　which　might　result　in　a　larger　granule　formed　in　R2.　This　study　clearly　confirmed　the　feasibility　of　granulation　of　PD　sludge　under　low　nitrogen　loads,　shedding　new　light　on　the　low-strength　nitrate　wastewater　treatment　with　an　efficient　and　economical　way.