Abstract: The performance-based seismic design is a developing trend of structure seismic design method. It is a revolution of the current seismic design procedures. This paper presents the performance objectives,performance levels,as well as the procedure to carry out the performance-based seismic design of mill building for conventional island of nuclear power plant. And seismic performance-based design method which is applied to mill building for conventional island of nuclear power plant is feasible according to a practical engineering case. The method and advice can be a reference to the engineering designers to design this kind of structures.