The metastable equilibrium solubilities and the physicochemical properties including refractive index, density, viscosity, conductivity, and pH for the aqueous reciprocal five-component system (Li + Na + K + Cl + SO4 + H2O) at 308.15 K were studied using the isothermal evaporation method. According to the experimental data, the dry-salt-phase diagram, sodium-phase diagram, water-phase diagram, and the diagrams of physicochemical properties versus composition were plotted. The dry-salt-phase diagram of the five-component system includes seven four-salt cosaturated points, fourteen univariant solubility curves, and eight crystallization zones all saturated with sodium chloride. Three kinds of double salts of lithium salts (Db1, Li2SO4 center dot 3Na(2)SO(4)center dot 12H(2)O; Db2, Li2SO4 center dot Na2SO4; Db3, 2Li(2)SO(4)center dot Na2SO4 center dot K2SO4) were found, and no solid solution was formed in the metastable five-component system. Because the Pitzer mixing ion-interaction parameters containing lithium and sodium such as theta(Li,Na), Psi(Li,Na,Cl), and Psi(Li,Na,SO4) at 308.15 K are scarce, the solubilities of the five-component system at 298.15 K were calculated on the basis of Pitzer's ion-interaction theory and the chemical equilibrium Harvie-Moller-Weare model (HMW model). A comparison of the calculated phase diagram at 298.15 K and the experimental phase diagram at 308.15 K was also carried out.