In order to solve the possible problems of decline bearing capacity and thawing of frozen soil resulting from future global warming in the design of pile foundation in Qinghai-Tibet Railway, thermal analysis model of ground temperature field for a single pile in permafrost was established based on the theory of heat conduction. Considering the condition that pile exposed in air absorbed solar radiation and transferred heat with natural air through convection, phase-change and global warming, ground temperature and long-term bearing capacity changes of a single pile in representative humid permafrost area in future 30 years were calculated and analyzed by using finite element method. The results show that in the coming 30 years, the natural geotherm and the temperature of the pile-soil system 3 to 20 m under the surface of the earth become higher as time goes by; the bearing capacity of single pile has the decline tendency in future. In 2040 summer, the bearing capacity will drop by 41.5% compared with the same period in 2010; in winter the bearing capacity will drop by 28.6% compared with the same period in 2010. The "dynamic factors"should be taken into account in basic pile design work in cold region in future. For the existing piles, reasonable and effective measures should be taken to improve the piles bearing capacity, which is key in solving the problems. 4 tabs, 12 figs, 20 refs.