Broken strand damage of the high-voltage cable may be caused due to environmental problems in use. And the existing detection technology cannot meet the requirements for detecting the broken strand damage of the part of the cable wrapped by the clamp on the high-voltage piezoelectric tower under the electrification condition. In order to solve the existing problems, laser ultrasound, a new non-contact laser ultrasonic detection method was adopted to detect the broken strand damage of a cable. The propagation of laser ultrasonic guided wave in high voltage cable was studied theoretically. The influence of small radius r, large radius R and axial pitch L on the dispersion curve of high voltage cable spiral structure was analyzed. A transient model was established to study the physical problem of laser excitation of ultrasonic guided waves in lossless cables. The amplitude and dispersion characteristics of the basic order modes L(0,1), T(0,1) and F(1,1) of helical structures were analyzed by means of B-scan and 2-D Fourier transform signal analysis. The results show that L(0,1), F(1,1) modes in the frequency range of 0 kHz~100 kHz are the most suitable detection modes when using laser ultrasound to detect high-voltage cables. This result is helpful to the research of non-destructive testing of high voltage cables by non-contact laser ultrasound technology.