Abstract: The mechanical behavior of unsaturated sands inevitably follows the principles of thermodynamics. By this method, we can study the hydraulic-mechanical behavior of soils with a general insight under a more universal law. Based on thermodynamical theory, and considering the relations among dilatancy, anisotropy and plastic dissipation of sands, a solid-liquid coupled constitutive modeling framework is established which can deeply indicate many complex behavior and properties for unsaturated sands.