To investigate the failure mode of tunnel crossing landslide body under earthquake action, a vibration platform test is conducted to obtain the acceleration time history curves of different positions in landslide body. Based on Hilbert′s marginal spectrum theory, the marginal spectrum of measuring points at different locations is obtained, and the peak value and characteristic frequency of each measuring point are extracted to reveal the failure mode of tunnel orthogonally crossing slide body. The results show the following: (1) When earthquakes occur at all levels, the orderly transfer of seismic energy in the bedrock does not cause seismic damage, while the incomplete transfer of seismic energy occurs first in the middle, upper, and lower slopes of the landslide. (2) The existence of the tunnel degrades the mechanical environment of the upper slope, resulting in the failure of the T16 measuring point at the top of the tunnel in the middle and lower slope under low energy input. (3) The vibration failure mode of the main sliding direction of the tunnel crossing slide body is collapsetesionslide failure.