Using isothermal dissolution method, the phase equilibrium relationship in quaternary system LiCl + NaCl + KCl + H2O and the ternary subsystem LiCl + NaCl + H2O at 288.15 K were investigated. Each phase diagram of two systems was drawn. The phase diagram of LiCl + NaCl + H2O system contains two solid phase regions of crystallization LiCl center dot 2H(2)O and NaCl. In the phase diagram of LiCl + NaCl + KCl + H2O system, there are three crystallization regions: LiCl center dot 2H(2)O, NaCl and KCl respectively. In this paper, the solubilities of phase equilibria in two systems were calculated by Pitzer's model at 288.15 K. The predicted phase diagrams generally agree with the experimental phase diagrams. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.