Abstract: The LiF-NaF and LiF-KF binary molten salt systems were assessed initially based upon the CALPHAD approach. The liquid and solid solution Halite phases were thermodynamically modeled by the substitutional solution model with Redlich-Kister polynomial terms. The model parameters were optimized by selected experimental phase equilibria information,thermochemical data,and present predicted data from the first-principles calculation. Whereafter,the thermodynamic database of the LiF-NaF-KF ternary system was established from the present assessed LiF-NaF and LiF-KF systems combined with the reported NaF-KF system through the Muggianu model with ternary interacting parameters optimized by the measured ternary eutectic point. It is demonstrated that the calculated results are well consistent with most of the experimental data and predicted data,which shows that the present thermodynamic parameters are credible and self-consistent and can allow accurate description of the phase equilibria and thermodynamic properties.