<p>The locked-segment slopes have garnered significant attention due to their extensive distribution and considerable destructive capability, particularly the three-section type of locked-segment slopes. Nonetheless, the existing research on the three-section type of locked-segment slopes under earthquake is limited, primarily focusing on acceleration and displacement response patterns, with few scholars examining the issue from an energy perspective. To elucidate the dynamic response and failure mechanisms of the three-section type of locked-segment slope from an energy perspective, this study extends numerical simulations for the previously conducted three-section locked-segment slope shaking table test using Hilbert–Huang transform and marginal spectrum theory. The results show that the amplitude and frequency of the input wave substantially influence the Hilbert spectrum and the marginal spectrum. The distribution properties of the Hilbert spectrum and the marginal spectrum along the frequency axis are concurrently influenced by the weak interlayer. There is a difference in total Hilbert energy between the sliding mass and the sliding bed, which is hypothesized to significantly influence the divergent seismic response characteristics of both, hence contributing to the occurrence of landslides. In addition, it is revealed that the deformation and failure mode of the three-section type of locked-segment slope is a progressive failure that develops from the upper part of the slope to the lower part, which can be generalized into three stages: local damage in the upper part of the locked segment, downward expansion of the damage in the locked segment, and damage through the locked segment.</p>