Abstract: Nonstationary structural response is currently an active area of interest in earthquake engineering. Low computational efficiency is problematic for nonstationary seismic responses of linear structures based on wavelet transformation. An improved method is thus proposed whereby seismic responses are obtained with time-frequency characteristics. Seismic signals were inputted directly into the structure and seismic responses were obtained by time domain analysis. The response of different scales and time-frequency characters of the seismic response were then reflected by wavelet decomposition and reconstruction. Using multi-resolution analysis (MRA) of wavelet transformation and modal analysis of the structural response, results from this new modified method were shown to be consistent with results of the existing conventional method. A numerical example illustrates the accuracy of the new method.