The dynamic electro-thermal operating characteristics of the quality-volume regulation in the wet-cooled high back-pressure retrofit unit were investigated, and the results were applied to the optimization of thermal power plant operation. The subcritical high back-pressure retrofit unit for heat supply was simulated and modeled using the Ebsilon software. By performing calculations under various operating conditions, the influences of main steam mass flow rate and extraction steam mass flow rate on the electro-thermal relationship were analyzed for two typical operating modes, i.e., pure back-pressure and extraction back-pressure. The objective was to determine the feasible operating region of the unit in terms of the electric-thermal relationship. In consideration of the unit’s actual operation primarily in pure back-pressure mode, the influences of the circulating water mass flow rate and inlet temperature change on the slope and operation range of the electro-thermal relationship during the quality-volume regulation of the heat network were further explored and quantified. This refined modeling approach provides a valuable tool for optimizing the operation of thermal power plants. Finally, the reliability of the above model was verified using actual operational data from a thermal power plant, and the coal-saving effect considering the dynamic characteristics of the unit on the plant-level load distribution was explored. The case calculation results showed that when the wet-cooled high back-pressure unit cooperated with condensing units to level the load distribution in plant, the feasible operation region model considering dynamic characteristics could map the power-heat relationship of the unit more accurately compared to the traditional linear model. The range of power generation for a 350 MW unit was expanded by approximately 2.37?4.24 MW under the same heating power, resulting in better economic efficiency of load distribution results.