To address the issue of misjudgment in leakage detection of underground diaphragm walls caused by conductive bodies such as H-beam joints, a tracer-assisted leakage detection method is proposed. The applicability of this method under the interference of conductive bodies is systematically investigated through a combination of physical model tests and numerical simulations. The research results indicate that when leakage and conductive bodies coexist, the potential response exhibits a superposition effect, with the conductive bodies dominating local potential distribution anomalies. As a result, the potential anomalies caused by leakage are weakened or masked in a single steady-state potential distribution, making them difficult to distinguish. By introducing a tracer and conducting time-lapse potential observations, the differences in the temporal dimension provide reliable criteria for effectively distinguishing between the two types of anomalies. The tracer-assisted dynamic potential detection method enables accurate identification of leakage locations, achieving reliable detection under the interference of conductive bodies.