The dielectric constant and the tangent loss were measured for the TeO2-P2O5 glass system in the frequency range 0.1-10 kHz at different isotherms. The dielectric constant and the tangent loss decreased with increasing frequency, while both of them increased with increasing temperature. The decrease of the dielectric constant with increasing frequency was attributed at low frequency to the contribution of all the polarizability components, while at higher frequencies the absence of ionic and orientational polarizability components. The increase of the dielectric constant with temperature was due to the combination of electronic, ionic and orientational polarizability components. The decrease of the loss factor with increasing frequency was attributed at low frequency mainly to the migration of ions in addition to the electronic polarization loss, while at high frequency the ion vibrations may be the only source of the dielectric loss, The increase of the loss factor with increasing temperature was attributed to the relaxation loss in addition to the conduction loss which increased more rapidly with temperature.