Abstract: Impelled by the “dual-carbon” targets, the transition toward a new power system dominated by renewable energy is accelerating. Nevertheless, conventional coal-fired power units encounter critical bottlenecks under deep peak-shaving operating conditions, characterized by insufficient operational flexibility and constraints on renewable energy accommodation. The latest research progress of Molten Salt Thermal Energy Storage （MSTES） technology coupled with coal-fired units is reviewed in this paper. The whole chain analysis is made from the dimensions of materials, equipments, system integration and operation control, in order to provide theoretical basis and technical support for related engineering applications. Initially, the thermophysical properties of four mainstream molten salt systems are synthesized, with particular emphasis on the compatibility between various molten salts and coal-fired units across different temperature ranges, alongside advancements in salt synthesis optimization. Subsequently, structural evolution and heat transfer enhancement mechanisms in key equipment—specifically molten salt tanks and heat exchangers—are examined. Then, the multi-source heat integration mode and control strategy of the coupled molten salt heat storage system in coal-fired units are presented in steady-state and dynamic operation models. The flexibility evaluation indexes such as peak load regulation depth, ramping rate, round-trip efficiency and exergy efficiency are analyzed. Economic and environmental evaluations of existing demonstration projects reveal that MSTES integration significantly mitigates wind and solar curtailment. Despite high capital costs, the technology exhibits a short payback period and robust life-cycle economic viability. Looking toward large-scale deployment, future research should prioritize high-performance low-cost materials, whole-system dynamic optimization, and multi-energy complementary integration. Moreover, establishing sound capacity pricing mechanisms and carbon trading markets is essential to fully realize the regulatory value of flexible resources, fostering a virtuous cycle between technological advancement and market returns.