Abstract: Sodium chloride dissolved rapidly in the initial low-magnesium solution during the course of carnallite decomposition.With the decomposition process went，as the dissolution velocity of magnesium chloride was so fast that the saturation degree of sodium chloride in the decomposing solution was decreased，the sodium chloride in the previous solution was recrystallized and the crystallization of potassium chloride was impacted.The effect of high-magnesium solution on carnallite decomposition was discussed by calculating and analyzing phase diagram data through adding magnesium chloride solutions with different concentrations.Results showed that potassium yield was improved nearly by 1.1%，mass fraction of fine sodium chloride was reduced nearly by 30%，and carnallite decomposition rate increased by 1.2% through adding high-magnesium solution.

Key words: carnallite decomposition, high-magnesium solution, fine grain sodium chloride, potassium yield