Energy-saving and improving energy utilization efficiency are common concerned topics of the whole world. Control quality of reheat steam temperature is an important factor for thermo economy, which is mostly controlled by mankind and leads to uneconomical operation. One of the reasons is unsuitable controller parameters, causing by inaccurate models. In this paper, reheater model was established based on single-phase heat-exchanger thermal system dynamics. And parameters of the model were determined by design manual. Simulation on a 1000WM unit showed that, the model had good dynamic and steady performance.