Directional drilling technology has the advantages of strong crossing ability and controllable trajectory. In areas where traditional exploration is difficult to implement， directional drilling can leave the hole at a long distance to avoid ground obstacles and conduct exploration in the predetermined area. A certain urban tunnel is undergoing directional drilling in a densely built area. It is selected to leave the hole at a suitable distance at a suitable site， and drilling is carried out along the 1m below the tunnel floor through trajectory adjustment. At the same time， two branch holes are implemented in the upper part of the main hole. The core extraction process is used to perform interval core extraction for all sections， and geophysical tests such as micro motion spectral ratio method and borehole acoustic resistivity are completed. The maximum burial depth of the main hole is 69m， the footage is 650.75m， and the maximum deviation of the trajectory is 0.81m. The successful implementation of the project has proven that the combination of directional drilling technology and geophysical testing technology can make up for the shortcomings of traditional exploration methods， better expose the geological conditions of tunnel surrounding rocks， and provide an effective means for complex urban tunnel exploration. At the same time， it is recommended to develop clear and feasible technical principles and norms to promote the application of directional drilling technology in the field of exploration.