Two-sublattice model was applied to calculate the phase diagrams. Phase diagrams were evaluated for LiCl-KCl-PuCl3 and its sub-binary systems. Liquidus projection of LiCl-KCl-PuCl3 system was plotted. Solubility of PuCl3 in LiCl-KCl eutectic was 0.415 in mole fraction at 773 K.