According to some basic theories of physics of frozen soil, heat transfer, frozen soil mechanics and frozen soil rheology, a mathematical model for moisture, heat and stress analysis of frozen embankment is established, in which the moisture and heat field are interacted with each other, the mechanical properties of frozen soil is decided by soil temperature and a in-situ test creep equation of frozen soil is also introduced. Meanwhile, its finite element program is written. Then, an experimental section of Qinghai-Tibet is taken as example, and the thermal-mechanical stability of the embankment is studied in detail. Through comparing with observational data, it is found that, the proposed analytical model is correct and reasonable, and it can well describe and predict the long-term stability of the embankment of Qinghai-Tibet railway.