Abstract: The regeneration and utilization of La in its thermal reduction slag of rare earth metal are of great significance for the high-value utilization of rare earth secondary resources. In this paper, the roasting modification of lanthanum samarium slag (LaSlag) and the electrochemical reduction separation mechanisms of La/Sm in (LiF-LaF₃)_eut fluoride molten salt carrier were studied. The effect of cathode current density and temperature on the (LiF-LaF₃)_eut.-LaSlag electroreduction parameters (cell voltage, back electromotive force and overpotential) was explored to provide a basis for optimizing external reduction conditions. The results showed that all the lanthanum-samarium slag could be dehydrogenated to stable rare-earth lanthanum-samarium oxides by roasting modification at no less than 823 K. Within the temperature range of 1 223~1 323 K, during the electroreduction process of the（LiF-LaF₃)eut.-LaSlag system, as the cathode current density increased within the range of less than 4.0 A/cm², the cell voltage and overpotential of the system also gradually increased, while the anode effect period progressively shortened. When the current density was higher than 4.0 A/cm², its three electroreduction parameters tended to be stable. As the cathode current density remained constant, the effect of cathode overpotential and anode effect period was relatively small. Below 1 273 K, the cell voltage and back electromotive force decreased slightly with the increase in temperature, while they tended to be stable at temperatures above 1 273 K.