Corrosion of structural materials in molten fluoride salts is a key problem in the implementation of many technological processes and scientific research, in this regard, when studying the physicochemical properties of fluoride melts, special requirements are imposed on structural materials of electrochemical devices. In this work a method for measuring the electrical conductivity of molten fluoride systems in a conductometric cell with coaxially located electrodes was developed. The electrodes are made of glassy carbon, resistant to interaction with fluoride melts when exposed to high frequency alternating current. Internal electrode is the rod located coaxially inside the external electrode – the tube. The electrode system can be immersed to any depth, while maintaining a constant volume of the melt over a wide temperature range. Electrochemical impedance spectroscopy was used to measure the resistance of the investigated melt in the range of ac frequencies from 1 Hz to 105 kHz with an ac voltage amplitude of 5 mV. The coaxial cell was calibrated against molten CsCl in the temperature range of 660–880°C during heating and cooling. The temperature dependence of the constant was used to calculate the electrical conductivity of the studied oxide-fluoride systems: 0.565KF-AlF3 with a molar-fraction ratio {{{{x}_{{{\text{KF}}}}}} \mathord{\left/ {\vphantom {{{{x}_{{{\text{KF}}}}}} {{{x}_{{{\text{Al}}{{{\text{F}}}_{{\text{3}}}}}}}}}} \right. \kern-\delimiterspace} {{{x}_{{{\text{Al}}{{{\text{F}}}_{{\text{3}}}}}}}}} = 1.3 and (KF–AlF3)–Sc2O3 with a Sc2O3 content of 1, 2, and 3 wt %. The electrical conductivity values for the 0.565KF–AlF3 melt obtained in cells of different designs (coaxial, with parallel molybdenum electrodes, and with a BN capillary) coincide within 1%. The temperature dependence of the electrical conductivity of the (KF–AlF3)–Sc2O3 systems in the range 590–720°C has an inflection point corresponding to the liquidus temperature. The coaxial cell can be used for measuring the electrical conductivity of aggressive fluoride and oxide-fluoride systems in a wide temperature range, as well as in the heterogeneous region.