Abstract: A novel tracing apparatus includes an electromagnetic transmitting system, a multi-frequency transmitting antenna, electrodes, and a receiver. The electromagnetic transmitting system is at an upstream point and includes a generator and a transmitter having a capacitor; the transmitting antenna penetrates into a detected aquifer through karst collapse or a drill hole; the electrodes and the receiver are at a downstream point, and include two pairs of electrodes orthogonally distributed and located in a cofferdam formed by downstream water; and the receivers collect electric signals in the electrodes. The apparatus is based on good electrical conductivity of water, and can use electromagnetic signals as a tracer for rapid observation. Compared with traditional tracers, electromagnetic signals propagate fast in water, are stable in property, and free of pollution.