The isothermal evaporation method was employed to investigate the phase equilibria in the quinary system Li2B4O7 + Na2B4O7 + K2B4O7 + Li2SO4 + Na2SO4 + H2O at 273.15 K. The solubilities and densities of the equilibrated solution were measured. The crystalloid forms of the solid phase were determined using chemical analysis and ail X-ray diffraction method. Oil the basis of the experimental data, the stereophase diagram, the projected phase diagram saturated with Li2B4O7, the projected phase diagram saturated with Na2B4O7, and the lithium content diagram of the quinary system were plotted. The stereophase diagram consists of six invariant points, eighteen univariant curves, and eight crystallization fields corresponding to sodium sulfate decahydrate (Na2SO4 center dot 10H(2)O), potassium sulfate, lithium sulfate monohydrate, sodium tetraborate decahydrate (borax, Na2B4O7 center dot 10H(2)O), potassium tetraborate tetrahydrate (K2B4O7 center dot 4H(2)O), lithium metaborate octahydrate (LiBO2 center dot 8H(2)O), it potassium and lithium sulfate double salt (KLiSO4), and a sodium and lithium sulfate double salt (3Na(2)SO(4)center dot Li2SO4 center dot 12H(2)O). The double salt glaserite (3K(2)SO(4)center dot Na2SO4) is not found at this temperature. The salt borax has the largest crystallization field and can be easily separated from the solution. The lithium content changes irregularly along with the evaporation process, thus the lithium salts are separated in a dispersed way.