Molecular dynamics simulation (MD) has been done for a molten (Li, K)Cl mixture of the eutectic composition at about 700 K, 950 K and 1100 K and, for comparison, also for pure LiCl and KCl at about 950 K and 1100 K The atomic masses of half the Li + and K + ions have been set at 6.941 and 39.098, respectively. Self-exchange velocities (SEV’s) of these cations have been calculated. The Chemla effect is reflected by the SEV’s. The isotope effects of the SEV’s in the mixture increase slightly with temperature. The motions of the cations with respect to the adjacent CI - are classified into four modes: (1) an oscillating motion, (2) a leaving motion, (3) a wandering motion and (4) a coming-back motion. It is found that the velocity of the leaving motion is dependent only on the masses and the temperature, and independent of the kind of cations and the composition.