A thermokarst pond (40 m×50 m, the maximum depth is 1 m) in the Chalaping of Tibetan Pleatu was regarded as a research object. Based on the measured data, the temperature variations and characteristics of thermokarst pond and natural ground at the same depth were analyzed. The results indicated that, compared with the natural ground, the thermokarst pond had a longer thawed time, a shorter frozen time, and a special time with water temperature being about 4℃. Due to the solar short radiation and convective heat transfer, the water temperature gradient in vertical was large during the surface temperature being decreasing from 4℃ and in the frozen stage, and other stages the water temperature gradient in vertical was almost zero. The annual average temperature at the bottom of pond was higher about 6.4℃ than that at the same depth of the natural ground. Besides, there was a talik being about 14 m depth under the bottom of pond being developing with time, and the heat absorbed and released of soil under the pond were increased and decreased, respectively. The heat absorbed from the depth of 2.5 to 3.0 m under the thermokarst pond was about 19592.0 kJ/m² being about 230 times of that under the natural ground,the heat absorbed was 1.4 times of the natural ground, but the heat released was only 8.7% of the natural ground. So, the talik was the main heat resource to the deeper permafrost, and the thermal impact of thermokarst pond on the permafrost underlying was due to the decrease of heat released from the soil.