The paper presents a theoretical and experimental study of the three-component mutual system Na+ ,Sr2+||F- ,WO4 2-. In the theoretical part, geometric modeling of phase complex is carried out. The thermodynamic method, according to Hess’s law, confirmed the partition variant with three phase triangles NaF – SrF2 – SrWO4 , NaF – 2NaF•Na2 WO4 – SrWO4 , 2NaF•Na2 WO4 – SrWO4 – Na2 WO4 . In accordance with the chosen partition option, the simulation of the liquidus variants of the three-component mutual system Na+ ,Sr2+||F- ,WO4 2- has been carried out. The separation has been experimentally confirmed by X-ray phase analysis of a mixture of 50 eq% Na2 WO4 and 50 eq% SrF2 corresponding to the full conversion point. The main reactions of chemical interaction for mixtures corresponding to equivalence points are described. A series of polythermal sections has been studied by diff erential thermal analysis, as well as X-ray phase analysis and thermogravimetry, from which the directions to three points of non-invariant equilibria and the coordinates (composition and temperature) of the triple eutectic and two peritectic have been determined. The points of non-invariant equilibria are located in the phase triangles 2NaF•Na2 WO4 – SrWO4 – Na2 WO4 and 2NaF•Na2 WO4 – SrWO4 – NaF. The considered phase complex of the three-component mutual system Na+ ,Sr2+||F- ,WO4 2– is represented by five crystallization fields – sodium and strontium fluorides, strontium tungstate, 2NaF•Na2 WO4 compounds of incongruent melting and sodium tungstate. Theoretical and experimental consideration of the three-component mutual system Na+ ,Sr2+||F- ,WO4 2- showed that the dominant crystallization field belongs to strontium tungstate as a more refractory component. The minimum crystallization fi eld belongs to sodium tungstate. The system’s phase tree and data on melting temperatures and compositions of non-standard equilibrium points have been refi ned in comparison with the previously obtained data on the system.