The two quaternary systems NaBr-SrBr2-MgBr2-H2O and KBr-SrBr2-MgBr2-H2O at 323 K were constructed by the isothermal dissolution equilibrium method. The mass fraction of every component of the equilibrium liquid phase in the two systems at 323 K was calculated. The phase diagrams and water content diagrams were plotted in accordance with the Janecke indices of salts and water. The system NaBr-SrBr2-MgBr2-H2O at 323 K has two invariant points, five univariant curves, and four solid phase crystallization areas, which correspond to strontium bromide hexahydrate (SrBr2 center dot 6H(2)O), magnesium bromide hexahydrate (MgBr2 center dot 6H(2)O), sodium bromide (NaBr), and sodium bromide dihydrate (NaBr2 center dot H2O). The system KBr-SrBr2-MgBr2-H2O at 323 K has double salt (KBr center dot MgBr2 center dot 6H(2)O) without solid solution formation. It has two invariant points, five univariant curves, and four solid phase crystallization areas corresponding to strontium bromide hexahydrate (SrBr2 center dot 6H(2)O), magnesium bromide hexahydrate (MgBr2 center dot 6H(2)O), double salt (KBr center dot MgBr2 center dot 6H(2)O), and potassium bromide (KBr).