The experimental data of metastable phase equilibrium of Li+,K+//Cl-,B4O72--H2O quaternary system at 298 K were obtained and its metastable phase diagrams were plotted .This quaternary system is a simple eutecyic type one, no double salt and solid solution is found. The isotherm diagram consists of two invariant points, five univariant curves and four crystallization fields corresponding to K2B4O7·4H2O,KCl,Li2B4O7·5H2O and LiCl·H2O salts. It was found in the metastable equilibrium phase diagram that: 1) the crystallization speciations of lithium chloride, potassium borate, and potassium chloride are the same as those in the stable equilibrium one; 2) lithium borate terhydrate and its crystallization region that were found in the stable equilibrium phase diagram are replaced by lithium borate quihydrate.
