Abstract: Under the new power system, the share of renewable energy has significantly increased the demands for grid flexibility regulation, while the decline in thermal power capacity necessitates faster response and greater operational flexibility. Advancing thermal power flexibility transformation has become key to enhancing grid regulation and ensuring energy security. Hydrogen energy, with its advantages of being clean, long-term scalable, and high in energy density, offers a promising solution. By coupling hydrogen production, storage, and utilization with thermal power, deep peak shaving can be enhanced, and carbon emissions can be reduced, providing a low-carbon and high-efficiency pathway for thermal power flexibility transformation. This paper reviews policy trends and industry developments, examines the feasibility and prospects of hydrogen energy in improving thermal power flexibility, and analyzes the advantages of hydrogen storage-thermal power coupling compared to power storage–thermal power and heat storage-thermal power coupling. Unlike power and heat storage, which are limited by short-duration capacity or single-mode regulation, hydrogen storage coupling enables multi-timescale energy buffering, enhances electric–thermal synergy, and improves system scheduling flexibility. Additionally, this paper explores feasible design schemes, and addresses key challenges in structural design, process control, and evaluation mechanisms. Finally, this paper further investigates technical bottlenecks in hydrogen production-storage-use integration, such as energy flow coupling, dynamic matching, and safety constraints, and proposes potential solutions to support research, engineering applications, and large-scale deployment of hydrogen-enhanced thermal power flexibility.