The process of starting AAOB granular sludge under low temperature substrate (NH+₄-N, NO-₂-N (40±10) mg/L) was investigated. In this study, SBR reactor was used to gradually shorten the experimental cycle to start AAOB granular sludge, and the nitrogen removal rate and nitrogen load of the system were analyzed for the kinetic characteristics of anaerobic ammonium oxidation process at each stage. Meanwhile, the granular sludge morphology, average particle size, EPS content, and three-dimensional fluorescence characteristics of EPS were analyzed. Results showed that the experimental period was shortened (24 h→12 h→10 h→8 h), and the nitrogen load increased from 0.074 g/(L·d) to 0.204 g/(L·d). The Grau second-orders model better characterized the process of starting AAOB granular sludge. The matrix removal rate constant k₂ increased from 0.15 to 0.22, and the denitrification performance was gradually improved. The MLSS and MLVSS of the sludge were finally stabilized from 2 989 and 2 348 mg/L to 2 460 and 1 776 mg/L. As the reaction went on, the anaerobic ammonium oxide sludge fully utilized the matrix, and the granular sludge was gradually stabilized. The average particle size of the particles reached 410 μm. The PN content and the PN/PS value first increased and then tended to be stable, and they became larger as the particle size increased. The three-dimensional fluorescence component in the sludge EPS was analyzed by the PARAFAC method, which was composed of NADH, riboflavin, and humic acid.