In this paper

the computation formulas of the earthquake response spectra based on parabolic interpolation method are derived

and the visual expressions of the formulas are presented in detail. With equal step length of time to discrete the earthquake records

the successive computation formulas of earthquake response spectra are presented according to the idea founded by prof.Wang Qianxin in 1962 based on the parabolic interpolation method. By analysing the results calculated by these different methods

it is proved that the values of earthquake response spectra obtained by the method presented in this paper are more close to the analytic values than that of the exact computation method presented by Nigan and Jennings（1969）. At the same time

it is found that the values of the exact computation method are smaller than the actual values.