Abstract: This paper investigates a rock slope with height of 100m. It is an invalidated mine slope. The cliff side carving is going to be designed and constructed in this rock slope. But the complicated engineering geological structures will control the location and size of the cliff side carvings. Consequently, it is very important to investigate the development characteristics of faults, joints, kast caves, rock mass structures in this slope with valid methods. This paper studies the validity and some geological interpreting keys in applying the Electromagnetic Wave Tomography to investigating engineering geological conditions. As a result, the Electromagnetic Wave Tomography is able to investigate faults, karst caves and fissure zones, structure type of rock mass and zones in the slope. Furthermore, the change characteristics of rock electromagnetic absorption coefficient are valid to illustrate integrity zoning of slope rock mass. The result can provide the scientific evidence to the construction and design of complex geological slope.