Electrical conductivities of the gneiss samples with different chemical compositions [W<sub>A</sub>=Na<sub>2</sub>O+K<sub>2</sub>O+CaO=7.12 %, 7.27 % and 7.64 % in weight percent] were measured using a complex impedance spectroscopic technique at 623–1073 K and 1.5 GPa in the frequency range of 10<sup>−1</sup> to 10<sup>6</sup> Hz. In addition, conductivities of gneiss with W<sub>A</sub> = 7.12 % were measured at 623‒1073 K and 0.5‒2.0 GPa. The results indicated that the conductivities of gneiss markedly increase with the increase of the total content of alkali and calcium ions. The conductivity of gneiss and temperature conform to an Arrhenius relation at a certain temperature range. The influence of pressure on conductivity of gneiss is weaker than that of temperature, and the conductivity increases with the increasing pressure. According to the various ranges of activation enthalpy (0.35‒0.52 eV and 0.76‒0.87 eV) corresponding to higher and lower temperature regions at 1.5 GPa, two main conduction mechanisms were suggested to dominate the conductivity of gneiss: impurity conduction in the lower temperature region and ionic conduction (charge carriers are K<sup>+</sup>, Na<sup>+</sup> and Ca<sup>2+</sup>) in the higher temperature region. Finally, it was confirmed that gneisses with various chemical compositions can’t cause the high conductivity layers (HCLs) in Dabie-Sulu ultrahigh-pressure metamorphic belt.