Considering the climate warming and the atmosphere conditions along the line, the mathematic calculations of unsteady phase transition temperature field of three typical sections of the Moscow-Kazan HSR roadbed were put forward to analyze the temperature distribution and variation rules in the next lOyears. The results show: The higher the height of the roadbed is, the longer the heat dissipation process is. The deeper the depth of the roadbed is, the smaller the temperature amplitude of the periodic change is. There exists transverse differences. The maximum frost depths of the shoulders are greater than the center of the roadbed with the value up to 1.1 m. The maximum frost depths are in the range of 2.0~3.5 m. The melting process of the roadbed is bidirectional, and it begins on the early April. There is a phenomenon of frozen nucleus near the top of the roadbed, the shoulder and the toe position. Then the conclusions are proposed, the soil properties in the range of frost depths and the possible transverse uneven deformation resulted from the transverse differences should be paid more attention to.