Abstract: Based on the NLCG inversion results of CSAMT, resistivity anomaly of CSAMT data were divided into four types (type Ⅴ, type Ⅳ, type Ⅲ and type Ⅱ), four tunnels (route) in the lines were compared and one of them was recommended in the light of engineering geological condition- based extent of anomaly and hard rock. According to the rock classification results, we identified the distribution of fault fracture zone and karst area, and we also assessed the integrity of the rock. Verified by drilling and geological data, CSAMT exploration reached the desired results.