In response to the problem of locating defects in grounding grid flat steel conductors, the authors propose a novel method that utilizes the cross-correlation functions of the echo signals from two grounding grid flat steel conductors for time-frequency analysis, employing the Smoothed Pseudo Wigner-Ville Distribution (SPWVD) technique. By analyzing the time-frequency characteristics of the cross-correlation signals, the time delay and corresponding frequency of the defect signal can be determined. Based on the dispersion curve of the dominant mode of the defect signal, the wave velocity corresponding to the frequency is determined, and combined with the time delay and distance between two acceleration sensors, the defect position is accurately calculated. Experimental results demonstrate that this method achieves a relative error in defect position measurement of less than 10%. This approach effectively addresses the localization error issue caused by dispersion characteristics, providing a new pathway for accurate detection and localization of defects in grounding grid flat steel conductors.