Alkali metal halides are used as heat-storing materials, electrolytes for chemical power sources and solvents for inorganic substances. Using three-dimensional vector graphics software, a 3D model of the phase equilibrium states of the quasi-ternary system LiF-NaF-KCl, which is a stable triangle of the four-component reciprocal system Li+ ,Na+ ,K+ ||F-,Cl, was constructed. Based on the 3D model, the polythermal and isothermal sections and the polytherm of crystallization of the phases were constructed for the first time.