The vacuum vessel is the core component of the Chinese Fusion Engineering Testing Reactor (CFETR); its main function is to remove nuclear heating, provide safety shielding, and maintain a high-quality vacuum environment. Therefore, the safety of the vacuum vessel is of great significance to the CFETR, and examining its dynamic performance is necessary. However, the conventional finite element method takes too long to perform the dynamic analysis of the vacuum vessel, which greatly reduces the efficiency of the design and analysis. Based on the modal synthesis method, this study uses ANSYS software to establish a substructure model of the CFETR vacuum vessel. A modal analysis and harmonic response analysis are conducted, and their results are compared with those of the conventional finite element model. The results show that the substructure model not only has the same accuracy as conventional finite element models, but that it also greatly reduces the time of dynamic calculation.