We　present　a　start-up　method　for　complete　autotrophic　nitrogen　removal　via　the　nitrite　(CANON)　granular　sludge　process　by　controlling　the　DO　concentration.　More　specifically,　we　initially　increase　the　activity　of　anaerobic　ammonia-oxidizing　bacteria　(AnAOB)　and,　subsequently,　gradually　increase　the　activity　of　ammonia　oxidizing　bacteria　(AOB).　The　results　indicate　the　optimum　process　parameters　to　be　an　8　h　reaction　period　and　an　aeration/non-aeration　time　ratio　of　1.0　h/0.25　h.　These　conditions　maintain　a　high　activity　for　both　AOB　and　AnAOB　and　are　also　conducive　to　sludge　granulation.　Following　64　days　of　continuous　operation,　the　mean　particle　size　of　the　sludge　increased　to　992　µm,　while　the　proportion　of　granular　sludge　accounted　for　approximately　87.16%,　and　the　proportion　of　sludge　with　a　particle　size　≥　1000　µm　was　36.66%.　Both　AOB　and　AnAOB　became　the　dominant　bacterial　genera　in　the　CANON　reaction　system,　while　nitrite-oxidizing　bacteria　were　successfully　discharged　from　the　reaction　system.　©　2021