The phase equilibria in the quinary Na, K, Mg//Cl, SO4-H2O system at 25 degrees C were determined, and a total phase equilibria diagram of the system was constructed by means of the translation method. Structures of Janecke diagrams for the parts saturated with each of the 15 equilibrium solid phases were extracted from the constructed diagram. The phase equilibria in the system are comprehensively revealed in the obtained results in this work. The structures of the parts saturated with halite, glaserite, and schoenite agree well with the available literature data. There are 16 quinary invariant points saturated with four solid phases, 45 quinary monovariant curves saturated with three solid phases, and 43 divariant fields saturated with two solid phases in the quinary Na, K, Mg//Cl, SO4-H2O system at 25 degrees C. Nineteen out of latter 45 curves extend between the quinary invariant points, while the other 26 curves are formed by the extension of relevant quaternary invariant points into the overall quinary composition of the system.