Abstract: The isothermal evaporation experiment at 50 ℃ on the underground brine of Jiangling Depression was carried out. Results showed that sodium chloride，potassium chloride，ammonium chloride，and sassolite were crystallizated out sequen- tially during the isothermal evaporation process，i.e.NaCl→NaCl+KCl→NaCl+KCl+NH4Cl→NaCl+KCl+NH4Cl+B（OH）3.In the early age of evaporation，there was only NaCl（evaporation loss less than 83.83%），in the medium age of evaporation，KCl and NH4Cl began to salt out（evaporation loss was at 83.83%~94.61%），and in the end，B（OH）3 started to crystallizate out （evaporation loss more than 94.61%）.Also，the concentration of lithium，rubdium，cesium，iodine，and bromine were enriched greatly in the old brine.The study provided an important basis for comprehensive utilization of this underground brine.

Key words: Jiangling Depression, underground brine；isothermal evaporation；salt crystallization law