<p>Groundwater is a key element in underground engineering and hydrogeological protection. Detecting its extent and migration is essential for engineering disaster prevention and water resource management. The traditional mise-à-la-masse method uses direct current (DC) or low-frequency alternating current (AC) to charge groundwater, but suffers from poor data richness and low detection efficiency. To address the problems with the traditional method, this paper proposes a mise-à-la-masse method based on multi-frequency pseudo-random signals. By synchronously transmitting multi-frequency pseudo-random signals with uniform fundamental frequency energy distribution to underground low-resistance bodies, multi-frequency potential responses on the ground are continuously received. On the basis of the differences in induced polarization effects observed at different frequencies, the percent frequency effect parameter is calculated. Combining the high potential value results and high percent frequency effect values presented in the low-resistance range by COMSOL simulation enables exploration of the extent and migration of underground low-resistance bodies. This method has been successfully applied in the field exploration of the Baiquan Spring region, Jinan City (China). The results show that: (1) The high-potential area around borehole 1 extends at points 17, 18 and 19, indicating that the direction of groundwater flow is from southeast to northwest. (2) The results of potential and percent frequency effect indicate that the slurry diffusion area is primarily concentrated around points 8, 9, 11 and 13 on the southeast side of borehole 2. Combined with potential gradient extrema, the slurry diffusion radius is estimated to be 3.55 m.</p>