The gneiss layer (body), a universal physical layer found across the Earth’s continents, has a low wave velocity and high electrical conductivity. Research on the properties of this layer, particularly the P-wave velocity and electrical conductivity, contributes to a better understanding of the mid-lower crust of the Earth. It also allows us to explore the mechanism of seismicity due to its relationship with the earthquake center location. Previous work on the P-wave velocity and electrical conductivity of rocks at high temperatures and confining pressure has provided fundamental results. In the current study, we collected P-wave velocity and electrical conductivity data of gneisses with temperature and pressure from research based in China as well as at the global scale. Results reveal the P-wave velocity to increase with pressure. Moreover, we determined regimes that result in low P-wave velocity and high electrical conductivity in the gneiss stratum. In order to fully implement our results, further research is required in areas such as the mutation and the transition pressure under increasing P-wave velocity.