Abstract: To investigate the dynamic characteristics of a supercritical coal-fired power unit under different peak shaving conditions during high-pressure heater (HPH) bypassing, a dynamic model of a 600 MW supercritical reheating unit was established based on the Dymola platform. The model was validated against field test data to ensure accuracy. The dynamic behaviors of boiler-side and turbine-side components were analyzed under various peak shaving scenarios after bypassing the HPH. The results indicate that bypassing the HPH leads to a maximum load increase of 34.18 MW under normal operating conditions. As the operating load decreases, the load increment also diminishes, measuring 23.66, 17.78, and 13.98 MW at progressively lower load conditions. The duration of load increase grows longer with decreasing load, extending to 450, 600, 800, and 1100 s, respectively. After bypassing the HPH, the feedwater flow initially decreases and then rises, while the main steam flow decreases with a delayed response. The maximum reduction in main steam flow under different load conditions is 15.28, 9.24, 5.82, and 4.15 kg/s, respectively. The reheated steam flow first increases, then decreases, and finally rises again. In terms of temperature, the main steam temperature first increases and then decreases, while the reheated steam and feedwater temperatures drop. The response time for steam and water flow as well as temperature increases with decreasing load. Additionally, the wall temperature of the water-cooled wall gradually declines as the load decreases. The highest wall temperature occurs at the top of the spiral water-cooled wall. However, at the initial stage of HPH bypassing, the water-cooled wall temperature experiences a brief rise, with the maximum increase of 6.25 °C observed at 50% THA (Turbine Heat Acceptance). This temperature rise lasts the longest, up to 500 s.