Abstract:The fractures network in the bedrock are the main pathways for the ground water getting in and the radioactive nuclides escaping from the nuclear waste repository which was built in the lowpermeability bedrock. So, it is very important to study the characters of the fractures networks to ensure the safety of the nuclear waste repository. The article analyzed the effects and abilities for using highdensity Electrical Resistivity Tomography (ERT) to indentify the threedimensional fractures networks in the different states bedrock insitu, by the field experiments which were done in the granite. The results indicate that it is feasible to identify the fractures networks in the bedrock for which the electrical property is highresistivity. And the resistivity around the fractures can reflect the positions of spatial distribution and the shapes of fractures very well. But the effects and abilities of recognizing the fractures networks are related to the measurementsdirection.