Abstract: By decreasing the settling time,aerobic granules enriched with phosphorus accumulating organisms(PAOs) were cultivated under alternate anaerobic/aerobic conditions in a SBR inoculated with conventional activated sludge.The system underwent three phases: rapid start-up with synthetic wastewater(phaseⅠ),stabilization with real domestic wastewater(phaseⅡ) and enrichment of PAOs by increasing ρ(P)/ρ(COD)(phase Ⅲ) and stabilized during 352 cycles.However,filamentous sludge bulking happened during start-up phase and readily biodegradable organics in synthetic wastewater was considered to be the main reason for filamentous overgrowth in aerobic granules.It was ultimately controlled through changing the substrate from synthetic wastewater to real domestic wastewater.The matured aerobic granules had an approximately spherical shape with a size of 0.8 mm,SVI of 17-30 mL/g.The average PO₄^3--P removal efficiency was above 90%.FISH analysis showed that PAOs accounted for about 51.48% of the total bacteria.