One-stage autotrophic nitrogen removal process was started up in two identical EGSB (expanded granular sludge bed) reactors feed with synthetic wastewater with NH₄⁺-N of 100~130mg/L, which were inoculated with flocculent nitrification sludge and anammox (anaerobic ammonium oxidation) granular simultaneously or in sequence, respectively. As the result showed, the reactor inoculated in sequence (reactor 2) had obviously more advantages than that inoculated simultaneously (reactor 1) on the start-up duration and nitrogen removal performance. The duration of activity inhibiting phase in reactor 1was almost twice than that in reactor 2, and the TN (total nitrogen) removal rate was also lower in reactor 1. As to the activity increasing phase, the start-up duration of reactor 2 was only 40 days, which was 8 days shorter than that in reactor 1. So the steady phase was achieved easier in reactor 2 than in reactor 1, meanwhile, the highest removal rates of NH₄⁺-N, TN and nitrogen loading removal (NLR) in the steady phase reached 84.1%, 68% and 0.49kgN/(m³·d) in reactor 2, respectively, which were higher than those of 79.1%, 65.1% and 0.45kgN/(m³·d) in reactor 1, respectively. FISH result showed that AOB (ammonia oxidizing bacteria) and Anammox bacteria dominated both reactors, while the main undesirable community, NOB (nitrite oxidizing bacteria), and was suppressed successfully.