Abstract: This paper gives the electric models of different ground-medium contamination on the basis of many ground-medium contamination examples.Calculated by 2.5D finite element method(FEM),it gives the abnormal resistivity characters of different ground-medium contamination when monitoring with different arrays. By analyzing,the paper confirmed the best array to monitoring different groundmedium contamination.This text also analyzes the feasibility to monitoring different contamination degree of ground-medium by FEM and gives the data processing methods which can improve the resolution of the apparent resistivity section.