To detect the presence of a large 'brine source' in the deeper parts of Tibet's Baqiancuo Salt Lake area, and to understand its distribution characteristics, control factors, and material sources, 1∶ 15 000 AMT (audio magnetotelluric) detection was conducted. This involved 12 physical points in the water area, resulting in a four-layer resistivity model showing a 'high-low-high-low' pattern in the deep longitudinal direction. The results suggest that a group of normal faults exist in the southern region of the Salt Lake area, which act as both water storage and conduction channels, forming a brine conduction fault zone. The finding is compatible with the halogenated fountain at the fracture outcrop. By analyzing data from 9 wells, the range of shallow brine layer below the Salt Lake was identified, which corresponds to the first set of low resistivity layers with good continuity. These results suggest that the layer is a water-rich favorable layer. Finally, after analyzing the chemical composition and content of the brine, combined with Neogene magmatic activity and tectonic background, it is generally accepted that the source of the brine is related to volcanic activity. This study highlights the importance of using audio geodetic sounding as an effective method to study deep brine, and proves the feasibility and effectiveness of AMT in water exploration.