Abstract: To thoroughly understand the geological characteristics of potential concealed structures in open-pit slopes induced by external factors such as mining activities and rainfall, this study conducted field detection tests on open-pit slopes using a small-loop transient electromagnetic (TEM) system. Field tests demonstrate that the small-loop TEM system exhibited excellent vertical and horizontal resolution, effectively reflecting the electrical characteristics of concealed structures within slopes and the stratification interfaces of lithospheric materials. Accordingly, the small-loop TEM system proved fast and feasible in detecting open-pit slopes. Combined with layered spatially constrained inversion (SCI) technology, surface lithosphere investigations, and geological constraints of strata, the small-loop TEM system can qualitatively and quantitatively interpret the spatial locations and general morphological characteristics of subsurface concealed structures. These interpretations allow for the inference of the material composition and structural properties of the deep lithosphere and the identification of concealed structures in advance, thereby reducing the risk of open-pit slope failure.