Taking the thermokarst lake by the Hongliang River, a typical thermokarst lake in the permafrost regions of the Tibetan Plateau, as a case, the effect of thermokarst lake on the thermal regimes of soil and permafrost table under and around the lake is studied. The results show that the predominant lateral heat effect of the thermakarst lake changes the thermal regimes of the soils in the lakebed and the lakeshore. As a result, the surrounding soil thermal regime, affected by the thermakarst lake and the surrounding permafrost, is in a dynamic balance process. The thermokarst lake itself has less impact on the subsurface temperature and the permafrost table in the surrounding soils, but the thermal effect of thermokarst lake results in permafrost table rising and ground temperature rising in the margins of lakeshore. Therefore, the thermokarst lake has a great influence on the permafrost temperature and the permafrost depth for the surrounding soils, especially near the margins of lakeshore.