The molecular dynamics simulation has been carried out on molten quaternary systems (Li, Na, K, Cs)Cl and (Li, Na, K, Cs)F at 973 K for the various compositions in order to investigate the electric properties, i.e. the self-diffusion coefficient, the self-exchange velocity and the relative differences in the internal cation mobilities of Cs in molten LiCl-NaCl-KCl eutectic and in FLINAK melts. These results allow us to conclude that the self-diffusion coefficients and self-exchange velocities of Li+, Na+, K+ and Cs+ with reference to Cl- and F- become almost similar tendencies for each composition. We found it possible to enrich at up to x(Cs) = 0.4 similar to 0.5 in molten LiCl-NaCl-KCl eutectic and in FLINAK melts as well as LiCl-KCl equimolar mixtures.