In this paper, a new friction damper isolation system (FDIS) is suggested for isolated nuclear power plants (NPPs). Seismic responses of NPPs are accomplished by means of the finite element approach and setting up a representative multi-particle model of NPPs. Results in terms of time domain analysis show that response of structure supported by FDIS under small seismic are correspond to fixed structure, and perform similar properties as conventional isolated structure under large seismic. The yield force of friction damper is one of the important parameters which are related to responses and absorbing energy under seismic input energy in new isolated structures. Compared with cases of different yield level, responses of superstructures increase respectively with yield force, while displacements of isolation layer decrease effectively. The proposed new isolation system could be beneficial in enhancing the seismic safety of isolated NPPs.