According to the geological background, metallogenic conditions and petrophysical characteristics in the surveyed area, three-dimensional geological mapping was studied by Audio-frequency Magnetotellurics Method (AMT). Based on AMT raw data processing and inversion interpretation, the authors inferred the underground resistivity differences of lithology and fracture structure within 2 km from the contact zone. Combined with the geological data and drilling results, the authors hold that the audio magnetotelluric method is good for detecting the underground geological body, clearly recognizing the marker bed of geoelectric layer and its hierarchical structure.