The in-situ preparation of LiCl-KCl-ZrCl4 melt was investigated by the replacement reaction between Zr and CuCl in LiCl-KCl melt at 500 degrees C, and the reaction progress was also investigated by a series of electrochemical techniques, such as cyclic voltammetry, square wave voltammetry and open circuit chronopotentiometry. The electrochemical signals show that the concentration of Zr(IV) ions increases gradually and then reaches to the maximum value with the reaction time increasing from 0 to 180 min, while the concentration of Cu(I) ions decreases rapidly and drops to below the detection limit of the electrochemical tests. Meanwhile, the concentrations of Cu and Zr ions in the melt were determined over time by chemical analysis in the course of reaction. The results are in good agreement with the electrochemical tests. Finally, LiCl-KCl melts with (0.837 wt.% similar to 1.709 wt.%) ZrCl4 are obtained, and the final concentration of Cu(I) in the melt has dropped to below 0.025 wt.% when the reaction lasted for 180 min. (C) 2015 Elsevier Ltd. All rights reserved.