Abstract: For many geotechnical problems, such as development and utilization of geothermal resources, nuclear waste disposal and refuse landfills, we need to consider the effects of temperature on the properties of unsaturated soils. In order to describe the volume change and water retention behavior of unsaturated soils under thermo-hydro-mechanical coupling conditions more comprehensively, a fully coupled thermo-hydro-mechanical constitutive model for unsaturated soils is proposed. In the proposed model, the average soil skeleton stress, modified suction and temperature are taken as stress variables, while the specific volume and degree of saturation are taken as strain variables. The thermo-hydro-mechanical interactions are reflected through the yield surface equations and the coupling laws between yield surfaces by the model. The thermo-hydro-mechanical interactions mainly include the influences of temperature and saturation on mechanical behavior, the influences of suction and overconsolidation ratio (stress history) on thermal deformation, the influences of density, temperature and hysteresis effect on water retention behavior, and the influences of temperature, stress and hysteresis effect on deformation during drying/wetting process. The predictions are performed on the test results under different stress paths using the proposed model. The applicability of the model is verified by the comparisons between predicted and experimental results.