Some inversion errors may be caused either by the distortion effect of the localized conductivity heterogeneity or by the fact that line direction is not perpendicular to the structural strike in the AMT measurement. This study took Northern Guangxi area as the study area: The best orientation of principal axis was found by choosing suitable method to carry out the impedance tensor decomposition. The limited data were used to extract such information as one-dimensional and two-dimensional skew, and the dimensional characteristics of electrical structure were analyzed. Finally, the best orientation of principal axis was applied to the 2-D inversion, thus the resistivity inversion section that conforms to the actual geological conditions can be obtained. Drilling verification has demonstrated the effectiveness of this method, which can analyze the dimension characteristics of geo-electric structure better and identify hidden structures.