In this paper, the authors conducted electrical impedance spectra measurements parallel and perpendicular to foliation in dry gneiss at 1.0 GPa and 343~962 K within the frequency range of 0.1~106 Hz using a 1 260 impedance analyzer. The high temperature and pressure experimental results indicate that impedance spectrum strongly depends upon the variation of frequency and temperature. A comparison between experimental results with data derived from electromagnetic soundings indicates that the dehydration of amphibole-bearing gneiss may provide an alternative explanation for high-conductivity layer.