Abstract: Two groups of different mixed sludges, with one group including anaerobic granular sludges, malodorous river sediments and aerobic activate sludge (R1), and the other including anaerobic digested sludge, malodorous river bottom sludge and aerobic activate sludge （R2）,were used as inocula in two parallel ASBR systems treating actual municipal wastewater for 180~210 d. At the end of the experiment, the inner cultured sludge were observed by scanning electron microscope for analysis of their surface morphology. It was found that anaerobic ammonia oxidation (ANAMMOX) could be successfully achieved in the two systems. The ANAMMOX occurred after operation of 135 days. Additionally, removal efficiencies of NH4+-N(97.35%) and NO-2-N(99%) were observed at the stable stage in the R1 reactor. Comparatively, the R2 reactor took on notable ANAMMOX after 102 days’ operation, the averaged removal efficiencies of ammonia and nitrite were 93.17% and 99% respecfively during stable operation. Taken together, the mixed sludge of R2 can be deemed as a relatively ideal inoculum for the ANAMMOX reactor due to its quicker start-up. The electron microscopy results showed that the anammox bacteria may exist in ASBR reactor.