Abstract: The escalation in the installed capacity of renewable energy generation has led to a rise in peak regulation pressure on power grids, resulting in heavier peak regulation tasks being imposed on thermal power units, whose flexibility and peak regulation capacity have been found to be insufficient. A 350 MW supercritical coal-fired unit was taken as the research object, undergoing retrofitting with a molten salt/high-pressure water thermal energy storage system. A series of thermal storage and release strategies were proposed, and a compressed air energy storage (CAES) system was further coupled on the basis of the coupled composite thermal energy storage system to investigate the variations in peak regulation and thermal performance of the unit under different thermal storage and energy storage scenarios. Results indicate that during thermal storage phase, the optimal scheme involves the extraction of main steam and reheated steam for sensible heat absorption, and sensible and latent heat absorption, respectively, with a peak regulation capacity of 43.60 MW being achieved. During thermal release phase, the scheme in which feed water is heated by high-temperature molten salt to generate main steam, the application of high-pressure hot water is for preheating, and the bypass feed water of low-pressure heaters is heated, attains a peak regulation depth of 7.71%, enabling a more efficient enhancement of the power generation load of the integrated system. After being coupled with CAES system, the peak regulation capacity of the integrated system is observed to increase with the growth of the composite thermal storage load and CAES capacity, with the minimum load reaching 14.94% turbine heat acceptance (THA) load.