Abstract: It is necessary to calculate the thermal deviation coefficient and hydrodynamic characteristics of supercritical circulating fluidized bed boilers during deep peak shaving load to address issues such as tube wall cracking and over-temperature tube bursting caused by fluctuations in load and mass flow rate. A mathematical model for hydrodynamic calculation is established based on the water wall and water platen structure of the boiler, and the real furnace thermal deviation coefficient is computed using measurement data. The thermal deviation coefficients are calculated for 310 and 110 MW loads, while the hydrodynamic calculation is performed at 120 and 70 MW deep peak shaving loads. The results of the output steam temperature calculation at 120 MW load are verified against the measurement data and the hydrodynamic calculation at the 70 MW deep peak shaving load is examined. The calculation demonstrates that the thermal deviation coefficients of circulating fluidized bed boilers vary depending on the load, but remain consistent at similar loads. The boiler operation is secure and stable at 70 MW deep peak shaving load. The numerical research on the thermal deviation coefficients and hydrodynamic characteristics of circulating fluidized bed boilers under deep peak shaving load provides theoretical support for the flexible deep peak shaving optimization transformation of existing thermal power units.