Swimming　bed/aerobic　granular　sludge　technology,　using　front　reactor　packed　with　a　novel　acryl-fiber　biomass　carrier-biofringe　(BF)　combined　with　back　reactor　cultivating　aerobic　granules　and　a　settling　tank,　demonstrated　a　high-rate　treatment　of　domestic　wastewater.　System　was　startup　quickly　after　6　days　and　granular　sludge　began　to　form　after　16　days　operation,　biofilm　attached　on　BF　and　aerobic　granules　all　contained　large　amounts　of　biomass　,　which　was　rich　in　protozoa　and　metazoa,　it　showed　high　activity　and　effective　treatment　for　domestic　wastewater.　Even　hydraulic　retention　time　(HRT)　was　only　at　3.2　hours　with　average　CODCr　volumetric　loading　of　2.03　kg　/m(3.)d　and　NH4+-N　of　0.52　kg/m(3.)d,　90.9%　of　average　CODCr　removal　rate　and　98.3%　of　NH4+-N　removal　rate　were　achieved.　Average　mixed　liquor　suspended　solid　(MLSS)　concentrations　in　the　reactor　reached　5640mg/L　at　the　highest　during　operation　period,　the　average　ratio　of　mixed　liquor　volatile　suspended　solid　(MLVSS)　to　MLSS　reached　0.87,　which　showed　that　sludge　had　the　characteristic　of　high　activity.　Furthermore,　microscopic　observation　of　biofilm　and　aerobic　granules　revealed　much　presence　of　protozoa　and　metazoa　on　the　biofilm　and　suspended　sludge,　this　long　food　chain　can　contribute　to　the　sludge　reduction,　0.1755　kg　MLSS/kg　CODremoved　of　the　low　sludge　yields　obtained　in　this　experiment　was　only　about　50%　of　the　conventional　aerobic　processes.　The　mechanisms　of　aerobic　granules　formation　were　also　proposed　in　this　study.　It　supposed　that　four　kinds　of　granules　formation　mechanisms　were　simultaneously　included　in　this　system,　that　is,　mechanism　of　enwinding,　mechanism　of　absorption,　mechanism　of　interconnection　and　mechanism　of　Combination.