Abstract: An adaptable three-dimensional (3D) contact model is necessary to perform discrete element simulation (DEM)on unsaturated structural loess, in which the effects of adhesive force and chemical cementation bond have to be taken into account. A 3DDEM contact model is introduced to simulate the macroscopic and microscopic mechanical behaviors of unsaturated and structural loess by considering the effects of adhesive force and chemical cementation. Interparticle adhesive force is composed of van der Waals attractions and capillary forces. Both bond stiffness and strength are associated with the bond size to represent unrecoverable chemical cementation. By using the relationships between water content and suction, a new 3D contact model for loess is established considering the coupling effects of water content-void ratio-suction. The DEM is used to simulate the triaxial and wetting tests at different deviator stress levels and the results show that the 3D contact model can well reproduce the macroscopic mechanical behaviors of unsaturated structural loess.