Abstract: Capacity curves could be got from push-over analysis,however the structural displacements on performance points must be got from capacity spectra method.The current capacity spectra methods were graphical and iterative methods.This A numerical method was presented for getting the displacement on performance points without any iteration.Displacements of four RC frame structures on performance points obtained respectively from the numeric method and Chopra capacity spectrum method were compared.The results indicate that the numeric method is not only accurate but also simple.