There are 37 lakes in the Qaidam Basin: 1 freshwater lake, 6 brackish-water lakes, 2 saline-water lakes and 28 salt lakes.The pH value of salt lake brines is 7.014 on the average, and the average total mineralization is 340.75 g/1. Their water bodies belong mainly to the five-component equilibrium system, :Na, K, Mg//SO4, Cl-H2O, which can be further grouped into sodium-magnesium sulfate subtype, magnesium sulfate subtype, chloride transition subtype and chloride type water by their hydrochemical property. The salt lake brines of the first salt forming epoch (N2-Q3) were of the sulfate type. In the second salt forming epoch (Q3-Q4), some of them were of the chloride type.The pH value of brines decreases with the increase of total mineralization. The pH value is lower when the total mineralization is from 50-310 g/1 and higher when the total mineralization is from 310-355 g/l, however, when the total mineralization is higher than 355 g/1, the pH value decreases slowly again.The total mineralization of th There are 37 lakes in the Qaidam Basin: 1 freshwater lake, 6 brackish-water lakes, 2 saline-water lakes and 28 salt lakes. PH value of salt lake brines is 7.014 on the average, and the average total mineralization is 340.75 g / 1. Their water bodies belong mainly to the five-component equilibrium system,: Na, K, Mg // SO4, Cl-H2O, which can be further grouped into sodium-magnesium sulfate subtype, magnesium sulfate subtype, chloride transition subtype and chloride type water by their hydrochemical property. The salt lake brines of the first salt forming epoch (N2-Q3) were of the sulfate type. In the second salt forming epoch (Q3-Q4), some of them were of the chloride type. The pH value of brines decreases with the increase of total mineralization. The pH value is lower when the total mineralization is from 50-310 g / 1 and higher when the total mineralization is from 310-355 g / l, however, when the total mineralization is higher than 355 g / 1, the pH value decreases slowly again. The total mi neralization of th