Abstract: Collapse is one of the most common and serious geological disasters in the Loess Plateau of China. In this paper, the seismic wave velocity characteristics of the potential slope failure internal structure of Lishi loess are analysed in detail using the in-situ seismic wave testing through field drilling test. The results show that the seismic wave velocity in the vertical direction increases with the depth, while the seismic wave velocity in the horizontal direction gradually increases from slope surface to interior of the slope. Numerical simulation results indicate that the potential slope failure generates outward deformation due to the unloading rebound. The deformation increment is related to distance to the slope surface, the closer the distance, the greater the deformation increment. The decrease of density is an important reason for the difference of wave velocity in the potential failure. The study shows that the variation pattern of seismic wave velocity can reflect the internal structure characteristics of the potential slope failure, and thus can be a method in research on prevention and control of loess collapses.