Abstract: Isolation technology can effectively reduce the acceleration of the superstructure of the nuclear power plant (NPP), however, under the strong earthquake, the large displacement of the isolation layer may lead to pipeline breakage. In this paper, a negative stiffness damping (NSD) system was proposed based on the principle of surface motion and the prestressing spring expansion and contraction. The negative stiffness was achieved by the spherical hinge movement on the curved surface of the arch, and its viscous damping worked in the spring compression direction. The theoretical restoring force model of negative stiffness system was also put forward and its mechanical properties were analyzed. The negative stiffness device was designed and the static test was competed. The test results are highly consistent with the theoretical restoring force model. The comparative analysis of seismic responses between isolated structure with NSD nuclear power plant and that with isolated nuclear power plant was carried out. By comparing the seismic responses under different seismic wave inputs, the results show that the proposed NSD system can effectively reduce the upper acceleration response and isolation displacement response.