With the introduction of the "double carbon" strategy in China, the installed capacity of renewable energy generation increases constantly, and thermal power units play an increasingly important role in grid peaking. In order to study the feedback characteristics of steam parameters during load variation in thermal power units,a dynamic model of a 300 MW thermal power unit was established on the Dymola platform, and the common plant control configuration was embedded in the model to study the dynamic characteristics of the unit with different magnitude load changes and different rate load changes. The results show that during the same rate of load variation, the main steam temperature varies in a smaller range due to the embedded main steam temperature control system, and the range of reheat steam temperature is relatively large due to the absence of reheat steam temperature adjustment strategy, with a minimum of 529.0 ℃. During the same magnitude of load variation, the slower the rate of load variation is, the smaller the deviation of the main steam temperature from the rated value is, and the reheat steam temperature has the same trend at different variable load rates, and eventually reaches the same stable value.