Abstract: With the expansion of KCl production scale and excessive consumption of high grade potassium-bearing brine resources，the salt lake manufacturers，which adopting traditional solution mining-sun curing process to produce carnallite，are difficult to carry on due to long mineralization period，high production cost，and complicated operation.Taking low grade salt lake brine as the study object，and phase diagram as the guidelines，carnallite was prepared by vacuum evaporation and velocity-controlled crystallization process to study the rapid crystallization and mineralization technology.Results showed the carnallite with mass fraction of 13.82%~14.90%（KCl） could be prepared by the new process and the mineralization speed doubled than that the original process.In addition，the influences of magnesium/potassium proportion and water evaporation amount etc.on the yield and quality of carnallite were investigated.Results proved that it was feasible to employ vacuum evaporation and velocity-controlled crystallization process to produce carnallite.

Key words: low grade potassium-bearing brine, vacuum evaporation, crystallization, carnallite