Abstract: The phenomenon of leakage and water gushing often occurs during excavation of foundation pit, which endangers the safety of foundation pit and its surrounding environment.It is very important to detect the leakage and soil erosion area quickly and accurately and to plug the area with grouting when the danger of water gushing occurs in the foundation pit.In view of the low resistance characteristics of the excavation leakage and soil erosion area, this paper tries to apply the ultra-high density resistivity method to achieve the precise location of the excavation leakage and soil erosion area.Firstly, the geoelectric response rules of leakage and soil erosion areas are obtained by using the ultra-high density forward and inversion software ZZ-RINV2D.Secondly, the detection test is carried out on the foundation pit where the leakage danger occurs.The results show that the application of ultra-high density resistivity to the detection of soil and water loss area of foundation pit leakage has a certain feasibility, and the inversion results combined with geological data can quickly define the location of the leakage and soil loss area, and provide reliable technical support for grouting plugging.