The invention relates to a seismic instrument system of nuclear power plant, which is mainly used for monitoring the vibration condition of the plant area, the device and the workshop of the reactor structure in the nuclear power plant, responding, providing earthquake information for the operating personnel of the nuclear power plant and deciding the further operation. The invention uses a plurality of sets of sensors which are distributed to different positions of the plant area and the reactor structure workshop of the nuclear power plant for continuously collecting and monitoring the vibration condition of the reactor workshop. Once the generation of earthquake is detected, an alarm signal is transmitted immediately for notifying the operation personnel to adopt an emergency operation,preventing and reducing the damage caused by the earthquake, and ensuring the operation safety of the nuclear power plant. Simultaneously, the system records the whole data in the earthquake generation process and can analyze and evaluate the structure safety of the workshop for providing basis to determine the next-period operation.