Abstract: In order to locate the hidden leakage of underground diaphragm walls, the numerical simulation studies on the detection of leakage defects of underground diaphragm walls are carried out by using the cross-hole quadrupole method and the tripole method. The results show that the curve of change rate of the apparent resistivity is more effective than that of the apparent resistivity to identify the location of the hidden leakage. A quadrupole method is proposed to accurately detect the limit power supply pole distance and measuring pole distance of hidden leakage. When the power supply pole distance exceeds a certain distance, the quadrupole method can no longer detect hidden leakage. The tripole method can accurately detect the limit power supply distance and measuring distance of the hidden leakage. When the power supply distance increases, the tripole method can perceive the location of the hidden leakage, but the measuring accuracy of the tripole method decreases gradually. Finally, the feasibility of the cross-hole electrical method to accurately locate the leakage hidden danger of underground diaphragm walls is verified through the laboratory tests, which provides the effective reference for the subsequent similar projects.