Abstract: With the global energy structure transformation and the rapid development of new power systems, the installed capacity of new energy sources such as photovoltaics and wind power is gradually increasing, impacting the traditional energy structure dominated by thermal power. However, the randomness, volatility, and lack of inertial support of new energy sources also seriously affect the safe and stable operation of the power grid. The role of thermal power units as stabilizers in providing deep peak shaving for the grid is becoming increasingly prominent. China's thermal power units have insufficient deep peak shaving capabilities, and direct deep peak shaving faces issues such as low-load combustion, overheating of heated surfaces, thermoelectric decoupling, and reduced economic efficiency. Thermal storage technology is an important means for the flexibility transformation of thermal power units to achieve deep peak shaving. The current status of sensible heat, latent heat, and thermochemical heat storage technologies is first summarized based on different forms of heat. Then, it analyzes the characteristics, process principles, and development and application status of specific thermal storage technology routes for deep peak shaving of thermal power units. The mainstream technologies include hot water tanks, electrode boilers, molten salt heat storage, solid heat storage technology, and phase change electric heat storage. The study found that sensible heat storage has low costs and the highest technological maturity; latent heat storage has high energy storage density and nearly constant temperature during heat storage/release processes, and has begun large-scale demonstrations, making it a current research hotspot; thermochemical heat storage has the highest energy storage density but is still in the laboratory research stage. Hot water tanks and electrode boilers are the earliest technologies applied to deep peak shaving of thermal power, with simple processes and minimal modifications to the thermal power system, but they also have issues such as large footprints and lower quality of released thermal energy. Phase change heat storage technology has huge latent heat, can release heat at a constant temperature, and has good thermal stability, but the technology is not yet mature. Molten salt heat storage technology and high-temperature solid electric heat storage technology have high heat storage temperatures and have enormous engineering application potential in large-scale thermal power plants.