Abstract: In order to study the influences of meso-parameters on the macro-mechanical behavior of unsaturated soils under triaxial stress, based on the PFC^3Dprogram, the numerical triaxial tests on unsaturated soils under equal confining pressure and suction based on the Hill contact model, which can exert matrix suction, are conducted.The relationships between the deviator stress and the axial strain under different meso-parameters are obtained.The numerical simulation results show that the Young's modulus and the friction coefficient have the greatest influences on the unsaturated soils, while the Poisson's ratio and the damping constant have a minor effect on deviator stress axial strain curve.The initial elastic modulus of the samples increases with the increase of the Young's modulus and the phenomenon of strain softening appears as well.The relationship between the friction coefficient and the peak strength shows obviously positive correlation when other parameters keep the same.This study has a certain guiding significance for the parameter calibration of the meso-contact model for unsaturated soils.