The main reactions occurred was studied in five ASBRs (1-5) which had run at steady ANAMMOX. The organic carbon condition was kept up by means of the addition of glucose in the wastewater. The results reveal that aerobic nitrifing bacteria, denitnifying bacteria and ANAMMOX bacteria could coexist, and the aerobic nitrification reaction, the ANAMMOX reaction and the denitrification reaction could occur according to certain order in the reactors. The optimal ANAMMOX performance was achieved in reactor 1 which C/NH4+ -N was 1.7. On hour 41, COD removal, NH4+ -N removal and NO2- -N removal in reactor 1 were 100%, 81.7% and 74.4%, respectively.