Arctic thermokarst lakes are sensitive and have regional specific. The major amplitude in ecosystem features could be noticed for Yamal – quite sensitive region according to close permafrost border and increasing human loads. During summer 2018-2020 several lakes of southern (valley of the Erkuta River) and central (Neitinskiye lakes) Yamal had been studied. Erkuta lakes have a medial depth 5 m and are formed on river and marine terraces that effect on hydrochemistry; water consumption by indigenous people can change ecosystem status as well. Thermokarst lake on riverine terrace has conductivity 43-798 μS/cm. The maximum of conductivity and water temperature (+23.5°?) was in a hot summer 2019. The lake on a marine terrace had a strong stratification with halo- and thermocline on 4 m depth with conductivity value from 42 μS/cm on surface to 1300 μS/cm on the bottom with declining water temperature from 20°? to 8°?. The dissolved oxygen (DO) values were 11-13 mg/l with neutral pH. Neitinskie lakes have a thermokarst origin formed due to melting out of the dead fossil glacier ice. Tangabteito Lake depth reaches 35 m, temperature decreases from 13°? on surface to 6°? on bottom. Electro conductivity, DO and pH do not change significantly: 38-85 μS/cm , 9.5-11.6 mg/l and neutral pH correspondingly. Hereby, Yamal thermokarst lakes have numerous hydrochemical parameters that affected by their origin, current loads and climatic parameters. Studies supported by RFBR 18-05-60291.