Abstract: When the nuclear-powered ship encounters an impact load, especially in the vertical direction, the control rods of the reactor would be displayed to some extent, and the reactor activity and the output power of the reactor would be changed, and thus the normal work of reactor would be affected. This can greatly influence the safety of ship navigation even to broken-down ship. In this paper, a reasonable calculation model has been established to study the responses of the control rods including displacement and acceleration to a vertical impact.The effect of the fundamental frequency of the reactor and the actuation duration of the impact load on the displacement responses of the control rods has been also studied.