Abstract: A mathematical model was developed to describle the heat-water-salt movement in unsaturated frozen soils, The flow of the fusion latent heat was incorporated into the sensible heat flow equation and the mass transport induced by the phase change was incorporated into the liquid flow equation to account for the phase transformation,and by this way,the three inter-dependant partial differential equations for the heat-water-salt movement in unsaturated frozen soils were established A so called "soil freezing characteristic curve" , which describles the dependance of liquid content on the freezing temperature, was also established and determined in this study. The model developed can be applied for heat-water-salt movement both in frozen and unfrozen unsaturated soils.