Abstract: An expanded granular sludge bed(EGSB) reactor seeded with the mixture of flocculent nitrification sludge and anaerobic ammonium oxidation(Anammox) granular was started up to cultivate the ammonium oxidizing bacteria(AOB)-Anammox granular sludge under micro-aerobic condition.The mature AOB-Anammox granular sludge was successfully formed after performing of the EGSB reactor for58 days in terms of the high ammonia-nitrogen concentration and inorganic influent.Under the circumstance of synthetic domestic sewage,the performance of the sludge was testified and proven to be stable.The maximum removal rate of NH₄⁺-N and total nitrogen(TN) reached 92.3% and 71.2% ,respectively,along with the average nitrogen loading removal(NLR) reaching 1.237 kg·N/(m³·d).Results of SEM and FISH analysis show that the AOB-Anammox granular sludge is mainly structured by two types of microflora.More specifically,AOB are configured on the surface of the sludge intensively while Anammox bacteria are homogeneously distributed inside the granular.