Based on analyzing and summarizing the examples of applying the resistivity sounding method to the differentiation of the salt water bed from the fresh water bed in Ala'er basin, this paper emphatically discusses the relationship between the variation of the electric sounding curve and the mineralization intensity of the aquifer. It is pointed out that the characteristic points (e.g., inflection points) of the curve are key electric anomaly indicators for the correct differentiation of the salt water bed from the fresh water bed. The effectiveness and the application vista of this technique in differentiating Quaternary salt water bed from fresh water bed are also expounded.