Abstract: Numerical simutation for 3D model with deep structures was carried out by using 3D finite difference resistivity modeling method.2D inversion of calculated apparent resistivity profiles of pole-pole and symmetric four-pole sounding was studied.The result indicates that pole-pole system can resolve 3D structures if the hori-zontal interval of the center of 3D abnormal bodies is not less than the total depth of the center of the two structures.Under the same conditions,symmetric four-pole system has horizontal resolution better than pole-pole system,and pole-pole system has vertical resotution better than symmetric four-pole system.