Abstract: Using the calculations of linear digital filtering method, this paper affairms the existence of the specious phenomena in the resistivity togging of horizontal strata. and makes it clear that these phenomena occur only on the cross section with low-resistance conducting basement. In addition, it gives qualitative interpretation for their physical essence. The authors study emphatically the quantitative relationships between critical polar distance, maximum deviation of apparent resistivity, surface resistivity and thickness. As for the three-la yered section with low-resistance conducting basement, in case when the first layer is locally thickened, the boundary element numerical technique is used to calculate the apparent resistivity profile curve of symmetrical quadrupole which is larger than critical polar distance, and the results demonstrate convincingly the practical significance of the specious phenomena in data interpretation.