The successful application of the 3-D finite element method for numerical modeling makes it possible to study the lateral inhomogeneous body. This paper mainly discusses the influence of the lateral 3-D inhomogeneous body upon the approximate resistivity. The anomaly characteristics of the inhomogeneous body are shown by four kinds of resistivity sounding methods. The anomaly differences between the objective and the inhomogeneous body are also illustrated. It is pointed out that the influence of the inhomogeneous body is one of the chief causes responsible for the false resistivity anomaly.