In this paper, an impedance discontinuities localization for the nuclear control cable using the time-frequency domain reflectometry (TFDR) is proposed. By analyzing characteristics of the target cable, the reference signal is designed. To be prepared for on-voltage experiment, the reference signal is injected into the target cable via capacitive coupler. Using the Wigner distribution, the reflected signal from the impedance discontinuities is analyzed in time-frequency domain. To estimate instantaneous frequency (IF) of the signal, the Wigner-Hough Transform (WHT) is applied to the nuclear cable. Through the estimating time delay between the IF of the reference signal and that of the reflected signal, the impedance discontinuities localization can be measured. The experiment using the TFDR is carried out to localize the impedance discontinuities spot as the end of target cable. Through the experiment, the performance of the proposed TFDR system is verified.