The thermosyphon foundation formed by pouring concrete around the thermosyphon is often used in power tower in frozen soil regions. The working power of the thermosyphon varies with atmospheric temperature and soil temperature by the evaporation section. A three-dimensional finite element model of thermosyphon foundation was established in this paper,which based on the knowledge of frozen soil heat transfer and the field test of ground temperature of power tower foundation in the Wangkun-Budongquan Section of the Qinghai-Tibet Railway. Considering the global warming,frozen soil phase change,hydration heat release of concrete and the change of thermosyphon power,the thermosyphon power and the soil temperature around the pile are calculated by iterative method. The calculation results show that the calculated results are in good agreement with the measurement and can reasonably simulate the actual situation in the field well. The power of the thermosyphon varies with discontinuous wave,and the power in the initial stage is up to maximum 160.6 W,and the average working power in the second year is 7.0 W lower than that in the first year due to the influence of the temperature of the concrete entering mold and the hydration heat releasing. The thermosyphon pile foundation can effectively increase the cold reserves of the foundation; the maximum reduction of soil temperature may reach 2.1 ~ 3.0 ℃ and the average annual ground temperature can decrease 0.8 ~ 1.5 ℃. It also can shorten the soil refreezing time by 34% and will increase the permafrost table by 49 cm in the thirtieth year.