With large-scale integration of renewable energy into the grid, conventional coal-fired units are shifting toward deep peak-regulation. Oxy-fuel combustion circulating fluidized beds (CFB) offer low pollution and high carbon-capture potential, but their large thermal inertia and complex load-change mechanisms limit peak-regulation flexibility. In this study, a MW-scale oxy-fuel CFB pilot plant is modeled using a two-level approach: computational fluid dynamics (CFD) for detailed mechanisms and a heat and mass balance (HMB) model for system dynamics. The wide-load operation from 30% to 120% is investigated. Results show that during load reduction, the fluidization regime transitions from fast to bubbling bed. At 30% load, the dilute zone temperature drops by 72 K compared with 100% load, and the axial temperature difference increases. NO emission reaches its highest value of 70.2 mg/MJ at 70% load. The load change rate affects system stability. During load increase, the CO₂ concentration in the flue gas first decreases and then increases. With a load increase rate of 3% Pe/min, the disturbance amplitude of CO₂ is 1.58%, while during load reduction it reaches 3.14%. This study provides a theoretical reference for safe and stable operation of oxy-fuel combustion CFB boilers under deep peak-regulation.