The high-density resistivity method is a good means to identify the material characteristics of the big and long tunnels within the buried depth of 100～250 m. In this paper, the high-density resistivity method was employed to conduct the linking exploration work along a certain tunnel of the Bao-Lan Passenger Railway. The stratigraphic structure and general engineering geological situation along the tunnel were revealed through examination, and the interpretation is quite in accord with the reality, thus providing the basis for further construction.