Abstract: Taking the reactor building of NPP as an example, comparison analysis of seismic responses was carried out with and without base-seismic isolation technology by the finite element analysis software ANSYS. The results show that the floor response spectrum, acceleration response and seismic action of the reactor building in the horizontal direction can be effectively reduced after the application of base-seismic isolation. The overall displacement of reactor building in the horizontal direction is larger and mainly concentrated in raft foundation of the isolation while the relative displacement between the floors is very small, and the reactor building shows the characteristics similar to the rigid body displacement after the application of base-seismic isolation. This base-seismic isolation has a significant effect on the seismic response in the horizontal direction while the effect is not obvious in the vertical direction.