Microbial　interactions　between　Anammox　and　heterotrophic　bacteria　in　different　granule　distributions　in　an　Anammox　system　(AMX)　and　partial　denitrification　coupled　with　Anammox　system　(PDA)　were　analyzed　in　this　paper.　Candidatus　Brocadia　was　the　main　Anammox　microorganism　in　granules　of　1.0　＞　d　＞　0.5　mm　with　the　highest　abundance　of　21.5　%　in　AMX,　significantly　higher　than　the　maximum　proportion　of　2.3　%　in　PDA　sludge　＞　2.0　mm.　However,　the　total　nitrogen　(TN)　removal　of　77.9　%　in　AMX　was　lower　than　PDA　(94.0　%)　because　of　the　excessive　NO3-N　generated　by　nitrite-oxidizing　bacteria　(NOB).　Anammox　activity　could　be　stimulated　by　heterotrophs　via　simple　organic　carbon,　which　decreased　with　the　increasing　size　of　sludge　in　AMX　but　increased　in　PDA.　This　highlighted　that　regulation　of　the　distribution　of　sludge　size　and　organic　carbon　source　had　an　essential　effect　on　efficient　nitrogen　removal　of　Anammox　technology.