Synchrosqueezing wavelet transform can get better frequency resolution by reassigning the time-frequency representation of wavelet transform. However, the diffusion along frequency domain can be suppressed while the diffusion along the time axis cannot be overcome. To address this issue, an improved synchrosqueezing wavelet transform is employed to enhance the accuracy of estimated instantaneous characteristic parameters in both time and frequency directions where we highly focus on. Two numerical simulations and a cable test with linearly and sinusoidal varying tension forces are used to verify the effectiveness and accuracy of the proposed method. The results demonstrate that the improved synchrosqueezing wavelet transform is appropriate for identifying parameters of time-varying structures with both better time and frequency resolutions in a specific region.