Three different mixed sludges， including anaerobic granular sludge and aerobic activate sludge, river sediments and aerobic activate sludge, anaerobic digested sludge and aerobic activate sludge, were used as inocula in three parallel SBR systems treating typical municipal wastewater, respectively. It was found that the anaerobic ammonia oxidation (ANAMMOX)reactors could be successfully startedup after 150~180 days’ operation with the NH4+-N removal efficiencies of 88%, 80% and 85%, respectively. Moreover, all the NO2--N removal efficiencies of these reactors were more than 96%. Comparatively, the startup period of the seeding sludges, namely the mixed anaerobic digested sludge and aerobic activate sludge,was relatively the shortest. Therefore, the above mixed sludge can be considered a promising inoculum for the start-up of AMAMMOX reactor.