As a key infrastructure in the lifeline system, the safety of the Coal-Fired Thermal Power Plants (CFTPPs) under earthquake loading is not properly considered since a systematic optimization method for seismic design of CFTPPs is scarce. This paper presents a simple iterative method for globally optimizing the dynamic parameters of the typical CFTPPs, which can be considered a special type of tuned mass damping. In this paper, the fixed-point theory is first applied to a 2-DOF model of an actual CFTPP as a benchmark. Because the optimized parameters obtained from the fixed-point theory are roughly and cannot be used in practice, an iterative method based on the frequency domain analysis of a 3-DOF model of the CFTPP is then presented and used to obtain more detailed and optimized parameters, where the basic idea is to make extremum values of frequency response curve as small as possible. To show the potential of the proposed method, an illustrative example is introduced, and the results show that the presented method is effective in alleviating the seismic responses of CFTPPs. Compared to the classic fixed-point theory, the presented iterative method can handle multi-DOF models under different conditions but needs no complicated calculations, and this makes it possible to lead to a more efficient and precise seismic design of CFTPPs.