Abstract: This study explored the influence of fluctuating nitrogen loading rate on the stability and denitrification performance of AnGS and examined the efficacy of vacuum degassing in controlling sludge flotation. Microbial community analysis indicated Nitrosomonas as the predominant nitrifying bacteria with a relative abundance of 4.85%, Candidatus_Kuenenia as the main anaerobic ammonia-oxidizing bacteria with a relative abundance of 21.05%, and unclassified_Bacteria as the dominant denitrifying bacteria with a relative abundance of 14.59%. Overall, this study demonstrated the successful enrichment and symbiosis of ammonia oxidizing bacteria, anaerobic ammonia oxidizing bacteria, and denitrifying bacteria within the reactor.