Beryllium-containing halide melts can be used for electrolytic obtaining and refining of beryllium, in processing processes for the spent nuclear fuel. Information about the melting temperatures of salt mixtures is important for the organization of technological processes with their use. The complexity of the study of salt mixtures containing beryllium fluoride is associated with a number of factors, among which salt hygroscopicity, corrosion activity in relation to structural materials and the toxicity of salt vapor. In this regard, all preparatory operations were carried out in printed boxing, in the atmosphere of Argon. Differential-termic analysis (DTA) of samples is also performed in the atmosphere of the dry and clean argon. In the work, they used crucibles from platinum and oxide beryllium. These materials showed better resistance to corrosion in the studied molten saline media. The fusibility diagrams of the fluoride of beryllium with alkaline metals (Li, Na, K, Cs), built by the results of differential-termic and X-ray phase analysis, are given. The coordinates of eutectic points are determined. In the interval of changes in the concentration of beryllium fluoride from individual alkaline metal chloride to the corresponding eutectic, the measurement results are represented in the form of approximation polynomas of concentration dependence of the melting temperature of systems BeF2–MeCl (Me = Li, Na, K, Cs). The fusibility of the salt mixtures of eutectic of lithium and potassium chloride with fluoride of beryllium has been studied. The most fusible of the studied mixtures contains 35 mol. % beryllium fluoride and melts at a temperature of 331°С. The absence of triple connections in the studied systems is shown. To identify phases, an X-ray-dissection analysis was used, which showed the presence of alkaline metals in the solid phase of the corresponding chlorides of alkaline metals. Beryllium fluoride was determined by the characteristic peak of absorption on infrared spectra. The work uses the original methodology for distillation of beryllium fluoride obtained by the decomposition of ammonium fluoride. In view of the tendency of beryllium fluoride to glass formation, information about the melting temperatures of melting in this component of salt mixtures is of an evaluative character.