Abstract: The aim of this study was to screen for ammonia nitrogen-degrading bacteria, which adapt to the breeding environment of black soldier flies（Hermetia illucens）, in order to inhibit ammonia emissions during the breeding process of the insects. Using ammonium sulfate as the sole nitrogen source, bacteria in BSF frass were subjected to enrichment culture, followed by isolation, purification, and determination of the ammonia-nitrogen degradation rate of the strains to select ammonia-nitrogen-degrading bacteria. The compositional changes of the bacterial community in the frass during the enrichment culture process were analyzed through high-throughput sequencing. After the first enrichment culture, four strains were isolated from the frass, among which FJAT-48032 and FJAT-48033 showed 99.93% similarity to Providencia rettgeri and Providencia vermicola, respectively; FJAT-48034 and FJAT-48035 both exhibited 99.93% similarity to Pseudomonas aeruginosa. After six consecutive enrichment cultures, FJAT-48041 and FJAT-48042 were isolated from the frass, with 100.00% similarity to Lysinibacillus macroides. The strains with the strongest ammonia-nitrogen degradation activity were FJAT-48041 and FJAT-48042, which achieved an ammonia-nitrogen degradation rate of 73.03%-76.97% within 96 hours. The relative abundance of Enterobacteriaceae and Alcaligenaceae in the sample bacterial suspensions increased after enrichment culture. The abundance of Enterobacteriaceae dramatically rose from 0.03% before culture to 42.33% after the first enrichment culture, and further increased to 74.85% after three consecutive enrichment cultures. However, after continued enrichment, the abundance of Enterobacteriaceae decreased, falling to 48.52% after the sixth enrichment culture, which was still significantly higher than before enrichment.