High-conductivity anomalies of 0.1–1 S/m are widely distributed in the mid-lower crust of the Tibetan Plateau. Dehydration of amphibole-bearing rocks may play an important role in explaining these anomalies. To survey the anomalies’ origin, therefore, the electrical conductivities of amphibole-bearing samples, containing varying amphibole content, are measured at 1.5 GPa and 600–1300 K. Our experiments show that dehydration melting occurs at about 1100 K. Proton conduction and ionic conduction dominate the conduction mechanisms before and after dehydration melting, respectively. The dehydration melting of felsic rocks, containing 25 vol% of amphibole, is unable to account for the high-conductivity anomalies of 0.1–1 S/m. In contrast, the dehydration melting of garnet amphibolite, with an amphibole content higher than 60 wt%, can enhance the bulk conductivity to higher than 0.1 S/m under the lower-crust conditions beneath the Tibetan Plateau. The melt fraction of the garnet-amphibolite is estimated to be 3.8–36 vol% in the partial molten region based on a cube-model simulation.