The design draft of the deep-draft cylindrical offshore nuclear power platform is similar to the diameter of its main hull, which makes its principal dimension characteristics different from the existing cylindrical platforms. In order to explore its hydrodynamic performance, a computational analysis is carried out on the hydrodynamic characteristics and time domain dynamic response of the deep-draft cylindrical offshore nuclear power platform. The roll and heave free decay motions of the platform are simulated based on the Computational Fluid Dynamics (CFD) method, and the damping factors are obtained based on second order damping model. The Response Amplitude Operator (RAO) and natural periods of the platform are calculated based on the potential flow theory. Combined with the typical marine environment conditions in the South China Sea, the motion response performance and applicability of the platform are analyzed and evaluated. The results show that: the natural periods of heave, roll and pitch of the deep-draft cylindrical nuclear power platform are higher than those of the common waves; the surge motion of the platform is mainly affected by the second-order wave load, and the low-frequency characteristics are obvious; the heave and pitch motions of the platform are mainly affected by its natural frequency, and the heave motion also exhibits wave-frequency characteristics. The overall hydrodynamic performance of the platform is good, and it is suitable for operations in the South China Sea. The results of the study can provide relevant reference for the engineering applications.