A method that can simulate earhtquake wave based on the hydraulic design response spectrum and the relationship of power spectrum and mean response spectrum in the non-stationary input is presented. It can be used to modify the initial wave and reduce the error of high frequency. In order to solve the shift of velocity and displacement obtained by integraling acceleration, the Huang transform is used to obtain the intrinsic mode functions of acceleration. The lowest frequency intrinsic mode function is generally the mean value or trend of singals. The velocity and displacement obtainde by Integraling the acceleration which is deducted trend dont have the shift problem.