The electric conductivity of pyrophyllite was measured by means of Sarltron-1260 frequency and phase impedance spectroscopic analyzer under the condition of 1.0, 2.0 GPa and 873～1223 K and on the basis of microcosmic mechanism analysis. The experimental results indicate that (1) the electric conductivity of the sample depends on frequency, (2) the relationship between electric conductivity and temperature is in linear accord with the Arrenhius equation,and (3) the dehydration temperature of pyrophyllite is 1074 K and 1101 K at1.0 GPa and 2.0 GPa, respectively. A conclusion different from previous conclusions has been drawn, which holds that an inflexion appears after dehydration.