Abstract: With the transformation of China’s energy structure and the advancement of new power systems, the demand for deep load regulation of coal-fired units is becoming increasingly urgent. Circulating Fluidized Bed (CFB) boilers, owing to their favorable fuel adaptability and load regulation potential, have become important assets for deep peak shaving. However, under deep load regulation conditions, the hydrodynamic system of CFB boilers faces multiple safety challenges such as reduced cooling capacity, uneven flow distribution, deteriorated heat transfer, and intensified wall temperature deviations. To clarify the effectiveness and limitations of existing technical solutions and provide direction for future technological development, this study focuses on four aspects: the application of internally ribbed tubes in waterwalls, structural optimization of waterwall systems, management of waterwall temperature deviations, and reasonable operational mode switching at low loads. It systematically reviews current key technical approaches and engineering cases addressing hydrodynamic safety in CFB boilers during deep peak shaving. Regarding internally ribbed tubes, studies confirm their effectiveness in delaying heat transfer deterioration in subcritical and supercritical regions and significantly reducing the amplitude of wall temperature surges. The key for deep load regulation lies in balancing the operating mass flow rate at low loads with the minimum mass flow required to postpone heat transfer deterioration. For waterwall structure, a secondary-rising waterwall system incorporating “waterwall + water-cooled panels” effectively increases the mass flow rate at low loads, enhances the self-compensating characteristics of tube groups, and homogenizes the outlet working fluid temperature. However, attention must be paid to wall temperature deviations and flow distribution optimization in the water-cooled panels. In temperature deviation management, based on heat absorption deviations resulting from uneven thermal loads, the distribution patterns of heat deviation coefficients under similar loads can be used for prediction, thereby guiding combustion adjustments to actively improve furnace heat load uniformity. Concerning operational mode switching, systems equipped with boiler water circulation pumps can maintain low-load mass flow by switching to wet-mode operation, effectively controlling wall temperature deviations, though their operational economy and pump loss issues require optimization. Engineering case studies on subcritical, supercritical, and ultra-supercritical units demonstrate that through integrated technologies including internally ribbed tubes, secondary-rising systems, thermal deviation control, flue gas recirculation, throttling orifices, and pump systems, all types of units have achieved stable ultra-low load operation for deep peak shaving, verifying the effectiveness and integration potential of these measures. Ensuring hydrodynamic safety in CFB boilers during deep load regulation is a systematic project involving tube design, system structure, and operational control. Future research should focus on deepening the understanding of flow and heat transfer mechanisms in internally ribbed tubes under ultra-supercritical and variable-load conditions, and developing optimized tube designs better suited for wide-load regulation. Establishing an online prediction and control system for waterwall temperature fields based on digital twins is recommended. Furthermore, optimizing wet-mode operation strategies and developing automatic regulation systems using artificial intelligence and optimization algorithms will improve low-load operational economy. Through multi-technology synergy and intelligent integration, it is expected to further enhance the hydrodynamic safety limits, operational flexibility, and economy of CFB boilers in deep peak shaving, providing stable and reliable peaking support for the new power system dominated by renewable energy.