The results of the study of the interaction between the CeF3+EuF3 system and the salt melt NaCl–KCl by spectroscopic methods are presented. It was established that no significant changes occur with CeF3 ions upon dissolution in the NaCl–KCl melt. Instead, the transition of EuF3 into solution-melt, both individually and in the CeF3+EuF3 system, is accompanied by oxidation-reduction reactions with the formation of Eu2+. Diffuse reflection spectra of the samples – both bottom (insoluble sediment) and upper parts of the solidified salt melt in the UV range indirectly indicate the excitation of photoluminescence of Ce3+ and Eu2+ ions. On the other hand, the presence of absorption bands in the near-IR range of the spectrum (1900-2300 cm−1) confirms the preservation of a certain proportion of Eu3+ ions in the salt melt. The influence of various factors (composition of the solidified salt melt sample, excitation wavelength, previous and subsequent heat treatment, and composition of the medium) on the nature of the excitation and emission spectra of the samples was studied. A very intense 5d-4f luminescence of Ce3+ and Eu2+ ions (at 330 and 430 nm, respectively), mainly in the upper part of salt melts, and much weaker 4f-4f luminescence of Eu3+ ions were observed. Certain parameters were optimized to reduce the proportion of luminescence of Ce3+ and, especially, Eu3+ ions and to increase the luminescence of Eu2+ ions. Solidified salt solutions-melts of the NaCl–KCl–CeF3–EuF3 system are promising materials for the creation of solar ultraviolet radiation detectors.