Abstract：Qing-Tibet railway in building traverses 550 km-long continuous permafrost region. Railway embankment construction on permafrost will substantially disturb the balance of heat and mass transfer between the ground surface and atmosphere and cause the redistribution of underneath temperature field. The trend of permafrost evolution can be deduced and stability of railway embankment can be evaluated according to the distribution of underneath temperature field. Temperature was monitored after the Qing-Tibet railway embankment was formed. In this paper，finite element method is used to simulate the temperature field of railway embankment. Firstly，temperature data monitored in a whole freeze-thaw cycle is used as the original temperature field. Then，the new variable of enthalpy is introduced to solve the phase-change problem. Finally，ANSYS is used to simulate temperature field under embankment from the year 2003 to 2030. The computation results indicate that permafrost can be protected with enough height of embankment and insulation protection，whereas the natural permafrost table in undisturbed ground declines year by year with annual average increment rate of 0.02 ℃，and at the same time，the difference of temperature field distribution between the sun-slope and the shade-slope will cause non-uniform deformation of roadbed and cracking on the surface.
