The East Taijnar Salt Lake is an important LiCl deposit in brine of Qaidam Basin,China.To study on the variation characteristics of this ore deposit before and after mining is of great significance for the rational and sustainable utilization of lithium resources in brine.Base on existing borehole data（before mining） and the measured borehole data（after mining）,the hydrochemistry of the LiCl deposit,the structure of the ore body and the water-salt equilibrium characteristics of the mining area were compared and researched.The results indicated that the hydrochemical characteristics of the LiCl deposit changed obviously after mining,the phreatic brine was further concentrated,and the evolution generally attained the stage of potassium mixed salt（blodite） precipitation,and the grade of LiCl of the deposit was higher than that before mining.The evolution of the confined brine was changed to relative desalination,which lain in the transition zone between picromerite and blodite in the K⁺,Na⁺/Mg²⁺/Cl^-,SO₄^2--H₂O phase diagram at 25 ℃,and the LiCl grade of the deposit was lower than that before mining. After mining,the thickness and area of the phreatic brine deposit decreased greatly,and a discontinuous north-south ore bed was formed,which changed the original forms of continuous strip distribution before mining.There was no significant change in the confined brine ore body after mining.The original water-salt balance changed after mining,water quantity change ΔQ and salt quantity change ΔQ_c were -2.83×10⁸ m³/a and -3.331×10⁷ t/a,respectively,indicating that salt quantity was positive equilibrium,and salt minerals were continue to precipitate.The study could provide the basis for rational exploitation and scientific protection of mining area.