To　achieve　the　rapid　start-up　of　anaerobic　ammonia　oxidation　(ANAMMOX)　reaction　at　room　temperature　and　sludge　granulation,　a　small　amount　of　ANAMMOX　sludge　was　inoculated　by　an　upflow　biological　filter　reactor,　and　ANAMMOX　was　started　by　stage　variable　load　and　shortening　hydraulic　residence　time　(HRT)　operation　strategy.　The　reaction　was　evaluated,　and　the　nitrogen　removal　characteristics　of　the　biofilter　were　evaluated.　The　results　showed　that　the　biofilter　started　the　ANAMMOX　reaction　in　a　medium-temperature　(25-29)　environment　for　22　days.　After　97　days　of　culture,　the　total　nitrogen　volume　removal　rate　(NRR)　reached　5.64　kg•(m3•d)-1,　the　total　nitrogen　(TN)　removal　rate　was　close　to　80%,　and　the　average　particle　size　of　the　granular　sludge　was　4.5　mm.　High-throughput　sequencing　analysis　showed　that　the　biofilter　formed　a　layered　structure　of　nitrifying　bacteria-heterotrophic　bacteria,　anaerobic　ammonium　oxidation　bacteria　(AAOB),　and　AAOB-heterotrophic　bacteria　from　bottom　to　top.　The　various　microflora　synergistically　denitrified,　creating　a　low　dissolved　oxygen　(DO)　stable　environment　for　AAOB,　and　the　dominant　population　Candidatus　Kuenenia　(AF375995.1)　was　enriched.　In　addition,　the　removal　process　of　pollutants　along　the　path　and　the　characteristics　of　sludge　along　the　process　were　analyzed,　and　it　was　verified　that　the　sludge　in　the　reaction　zone　had　good　ANAMMOX　activity.　An　ANAMMOX-biofilter　reactor　achieves　rapid　start-up　of　the　ANAMMOX　reaction,　sludge　granulation,　and　efficient　operation　by　effectively　maintaining　the　amount　of　bacteria　and　stabilizing　the　reaction　conditions.　©　2020,　Science　Press.　All　right　reserved.