The value of δ³⁷Cl can be used to indicate the intensity of evaporation, possible sources and controlling factors during salt lake evolution. In this paper, 12 brine samples were collected and their chlorine isotopic compositions were analyzed. The results showed that the values of δ³⁷Cl range from -0.10‰ to 1.36‰, with an average value of 0.55‰. The values of δ³⁷Cl in the lakes of sodium sulfate type range from -0.10‰ to 1.36‰, with an average value of 0.56‰, and those of magnesium sulfate type are from 0.14‰ to 0.82‰, with an average value of 0.48‰. In comparison with the chlorine isotopic composition of brines in Qaidam Basin, it is found that the average value of δ³⁷Cl in the investigated area is greater than that in the Qaidam Basin. Among three brine types, the δ³⁷Cl values of sodium sulfate type brine are highest, those in the magnesium sulfate type brine are lower, and those in the chloride type brine are lowest. The evidences of the different salinization of groundwater, the δ³⁷Cl values of salt lake brine and the ratios of Br/Cl indicated together that the salt lakes located in the eastern and northeastern may be supplied by saline water from the Tertiary stratum, while the other salt lakes are mainly affected by evaporation. The distribution characteristic of the δ³⁷Cl values showed that the evolution of these salt lake brines may be affected by multiple factors such as tectonic activity-induced supplies of Tertiary deep waters and the water-rock interaction in Tengger Desert region.