Aerobic　granular　sludge　was　cultivated　in　three　column　reactors,　which　had　been　operated　for　120　days　under　different　feast/famine　ratio　(1:7,　1:11,　1:15).　The　composition　of　total　bacteria　was　analyzed　by　testing　oxygen　uptake　rates　of　mixed　liquor　samples　taken　from　the　reactors　and　calculating　according　to　activated　sludge　model.　The　results　revealed　that　long　famine　phase　favored　the　growth　of　heterotrophic　bacteria.　The　heterotrophic　bacteria　accounts　for　49.80,　53.37,　91.39%　of　total　bacteria　respectively　in　R-1,　R-2　and　R-3.　The　heterotrophic　nitrification　was　also　observed　in　all　the　reactors,　which　accounts　for　58.62,　58.33,　61.54%　of　total　nitrification　respectively　in　R-1,　R-2　and　R-3.　A　novel　nitrogen-removal　pathway　involving　simultaneous　nitrification-denitrification　by　heterotrophic　nitrification　bacteria　was　proposed.　The　results　revealed　that　microbial　system　consisted　of　heterotrophic　ammonia　oxidizing　bacteria　showed　stronger　capacity　of　simultaneous　nitrification-denitrification.