Abstract: Guided waves, as an effective non-destructive testing method, have a broad application prospect in steel strand inspection. Due to the special spiral structure of steel strands, the propagation characteristics of guided waves in steel strands are not yet fully understood. The frequency dispersion property of guided waves in a seven-wire steel strand is investigated. The spiral coordinate system is established by using the Frenet-Serret method, and the traditional semi-analytical finite element method is improved to obtain the waveguide characteristic equation applicable to the spiral structure. Then the dispersion curves of a single high-strength straight steel wire are calculated, and the dispersion characteristics of the guided waves are analyzed. Meanwhile the dispersion characteristics of the guided wave propagating in a seven-wire strand are investigated, and the obtained dispersion curves are consistent with the experimental results in terms of the central frequency of the "trapping" phenomenon. There is a great difference in dispersion curves between the steel strand and the straight steel wire. Experiments to test the steel strand ultrasonic guided wave stress were undertaken to verify the correctness and effectiveness of the spiral semi-analytical finite element method proposed in this paper. The results show that the analytical group velocity is in good agreement with the experimental results, and the axial stress of the steel strand has an approximately linear relationship with the guided wave group velocity in the steel strand.