In this paper the phase diagrams of LaCl3-LiCl and CeCl3-LiCl systems have been experimentally determined and theoretically calculated. Bath are simple eutectic systems. The eutectic points are at 25mol% LaCl3, 508℃ and 27mol% CeCl3, 494℃, respectively. The optimized phase diagrams and thermodynamical data of LaCl3-LiCl and CeCl3-LiCl systems with self consistency are a better basis for constructing ternary phase diagrams