Abstract: The electrochemical behavior of Li2O in KCl-LiCl molten salt has been studied by cyclic voltammetry and chronopotentiometry. The diffusion coefficient D=0.5×10^-5 cm²/s of O₂^- in KCl-LiCl molten salt at 923 K has been calculated by convolutional voltammetry. Gd₂O₃, Nd₂O₃, Sm₂O₃ and Dy₂O₃ were used as cathodes to conduct electrolysis in KCl-LiCl-Li₂O(w=1%) molten salt(constant voltage 3.40 V, electrolysis temperature 923 K, electrolysis time 25 h). By XRD analysis, it was confirmed that the rare earth oxides are partially reduced to metals, and the possible reactions during the electrolysis process were analyzed. At the same time, the PRS model was used to analyze the electrolytic reduction models of these rare earth oxides, and the optimal porosity(Popt) of Gd₂O₃, Nd₂O₃, Sm₂O₃ and Dy₂O₃ are 18.7%, 24.2%, 30.6%,16.7%, respectively. The minimum electrolysis time of them are 133, 157, 143, and 119 h, respectively, which are compared with the results of the electrolytic experiment, it is found that the porosity and electrolysis time of the cathode do not meet the requirements for complete reduction of metal oxides, and the corresponding explanation is given.