To address the challenge of accurately detecting water-bearing hazards ahead of the tunnel face in underground engineering projects threatened by gas and water inrushes, this paper investigates a small-current cascaded high-power borehole transient electromagnetic (TEM) exploration technology.By employing a multi-stage small-current cascade transmission method, the system achieves high-current transmission for borehole TEM within intrinsically safe (IS) limits, thereby enhancing the intensity of the secondary field signals excited in water-bearing bodies surrounding the borehole.Laboratory tests and field experiments demonstrate that this cascaded high-power advance detection technology achieves a single-stage transmission current exceeding 3A and a turn-off time of approximately 20μs. It attains a radial detection distance of 30 meters and an unlimited axial detection distance. This breakthrough overcomes the bottleneck of conventional roadway TEM, which is typically limited to an effective advance detection range of 80 meters, thus creating a sufficient time window for the early detection and mitigation of water hazards.