In this paper, unsaturated frozen soil moisture and heat transfer coupling model were estab-lished based on the theory of porous media.Assuming that the water migration process was one-wayand reversible and without solute transport, water transport equation of without and with phase transi-tion were derived based on nonlinear Darcy's law.Then the heat transfer equation in soil and thechange equation of quality of soil skeleton density were introduced into the model and in this process, the temperature variation during phase change of water in frozen soil and the interaction between tem-perature and quality changes were considered.At the same time, the effect of diffusion and convec-tion were taken into account too.Eventually the equation of water and thermal distribution of unsatu-rated frozen soil was got.And the method for determining the model parameters was given.Model e-quations are nonlinear partial differential equations, only numerical method but analytical solution canbe obtained.