The traditional linear frequency sweep method for cable defect location can generate abnormal peaks during FFT processing due to spectral leakage, interfering with defect identification. To address this, we propose a method based on exponentially increasing frequency reflection coefficient spectrum. Firstly, we replace linear frequency sweep with exponentially increasing frequency sampling, resulting in dense low-frequency and sparse high-frequency sampling, reducing spectral leakage in low frequencies. Secondly, low frequencies have concentrated energy and slow decay, leading to higher amplitudes after FFT, while high frequencies have dispersed energy and fast decay, resulting in lower amplitudes. Thus, even if spectral leakage increases in high frequencies due to sparse sampling, it does not exceed the main lobe amplitude, achieving suppression. Finally, validation on a 500 m laboratory cable shows that this method flattens amplitudes outside impedance mismatch points in the positioning curve, effectively suppressing abnormal peaks, confirming its effectiveness.