Abundant underground brine resources are in the Dazhou area of eastern Sichuan,with reserves of about 8.23×10⁸ m³,which are rich in sodium,potassium,lithium,boron,rubidium,bromine and other elements.The change of pH,the en-richment regularity and salting out law during the process of isothermal evaporation at 75 ℃ of the brine was investigated in the experiment.The types of precipitated salts were detected by XRD,and the precipitation order of salts was determined.Ex-perimental research results showed that the solution pH decreased with increasing loss rate.Sodium chloride largely precipi-tated in the whole evaporation process.Potassium began to largely precipitate as potassium chloride when the evaporation rate reached 77.3%.When the evaporation was near the end,both calcium and boron were partially analyzed.The order of appear-ance of the salt was：sodium chloride→sodium chloride+potassium chloride→sodium chloride+potassium chloride+boric acid.The law of evaporation was the same as the phase diagram of K⁺,Na⁺,Mg²⁺//Cl^--H₂O（75 ℃）.Preliminary design of the process route for the utilization of brine resources was based on the evaporation experiment data.The research results provided reliable basic data for the development and comprehensive utilization of underground brine in eastern Sichuan.