Abstract: Objective About exploring potential faults, some basic characteristics of a fault and groundwater are revealed, which is significant in geo-technical engineering. Materials and Methods Resistivity tomography has been widely used in exploring potential faults. In general, two sides of a fault have different resistivity features. However, from resistivity distribution in resistivity image,resistivity tomography is often difficult to distinguish a fault from a formation bearing groundwater, because both of them have low resistivity values and have quite similar anomalous patterns. Result It is found that the pattern of groundwater always shows horizontal extension or/and dumpling pattern in local regions, which is quite different from that of a fault with nearly vertical linear structure and good horizontal continuity. Also, there is a common tendency that the depth of groundwater layer in all profiles gradually increases towards a certain direction. Conclusion It is interested that the resistivity image of groundwater can have season抯 variation. Some applications of resistivity tomography in geo-technical engineering are presented and discussed in this paper.