Abstract: With salt pan process of Chaerhan Salt Lake brine teds to sodium-contaning carnallite as the research object，based on Na+，K+，Mg2+∥Cl--H2O quaternary salt system phase diagram theory，the isothermal phase diagram at 25 ℃ and multitemperature phase diagram of Chaerhan salt pan process were analyzed.Results showed that the crystallization routes of Chaerhan Salt Lake brine were NaCl→NaCl+Car→NaCl+Car+Bis at 15~25 ℃，and NaCl→NaCl+KCl→NaCl+Car→NaCl+Car+Bis at-5~15 ℃，respectively.Material balance showed that stage evaporation made sodium mass fraction of crude ore decrease from 37.046% to 12.353%，potassium mass fraction increase from 16.899% to 23.525%.Stage evaporation could effectively reduce the impurity NaCl in carnallite and increase carnallite grade. KCl′s yield was up to 97.90%.This study could provide theoretical guidance for salt production and process calculations.

Key words: Chaerhan Salt Lake, salt pan process, phase diagram, material balance