This paper investigated the denitrification performance and stability of aerobic granular sludge (AGS) for treating inorganic wastewater with high ammonia nitrogen in a continuous flow reactor. The reactor was started by seeding with mature AGS. The influent nitrogen loading rate was gradually increased from 1.0 kgm-3d-1 to 4.0 kgm-3d-1 in the former 55 days, gradually decreased to 1.4 kgm-3d-1 in days 56~125, and then increased to 2.0 kgm-3d-1 again in days 126~145. In the former 75 days, obvious particle breakage and sludge loss were observed, and the average particle size decreased continuously. Although seed AGS was supplemented several times to maintain the stability of the system, the sludge volume index (SVI), extracellular polymeric substance (EPS) and specific oxygen uptake rate (SOUR) of the granules fluctuated sharply in the former 90 days. Affected by the epidemic, the reactor was idled in situ in days 91~109. After re-startup, the physical and chemical indexes of AGS tended to be stable gradually. The removal efficiency of NH4+-N gradually increased to more than 98% in the former 45 days, rapidly decreased to approximately 50% in days 46~75, and then rose to more than 99% again. The total inorganic nitrogen removal efficiency was between 35% and 45% in most of the days. The selective screen of sludge was investigated by sludge interception test. When the depth of the baffle in the sedimentation tank was 27 cm, the sludge retention rate of the reactor was above 98%, and the particle size of sludge in effluent was mostly between 0 and 0.30 mm. The microbial community of sludge was analyzed by high throughput sequencing. Compared with the seed AGS, the relative abundance of nitrifying bacterial genus (Nitrosomonas) in AGS on day 145 increased significantly, while the relative abundance of denitrifying bacterial genera (such as unclassified_Flavobacteriaceae, unclassified_Xanthomonadaceae and Thauera) decreased slightly.