A novel molten salt synthesis route has been developed to prepare ternary La1-xCexB6 (x=0.2, 0.4, 0.6, 0.8), using LaCl3, CeCl3, and NaBH4 as reactants and eutectic LiCl/KCl salt as molten salt medium. All the synthesized ternary La1-xCexB6 are single-phase solid solution, and their lattice constant decreases linearly with increasing x. Morphology, microstructure, and elements composition of La0.6Ce0.4B6 which is a typical representative of the series of La1-xCexB6 are analyzed in detail.