Abstract: The interparticle bonding effect has a significant influence on the hydro-mechanical coupling characteristics of unsaturated soils. Establishing a constitutive model for unsaturated soils considering the bonding effect is of great significance for accurately analyzing their hydro-mechanical coupling characteristics. Based on the theory of bounding surface plasticity, a hydro-mechanical coupling model for unsaturated soils considering the influences of matric suction, degree of saturation and pore structure on the bonding effect is established. For the mechanics part, the effective stress and bonding variable are selected as the constitutive variables, the relationship between the bonding variable and $e\text{/}{e}_{\text{s}}$ is established, and the deformation characteristics of unsaturated soils are described based on the theory of bounding surface plasticity. For the hydraulic part, a hydraulic hysteresis soil-water characteristic curve equation considering the effect of deformation is established. The experimental results of bentonite-kaolin mixture and reconstituted kaolin are used for parameter calibration and model verification of the proposed model. The results show that the proposed model can reasonably predict the hydro-mechanical coupling characteristics of unsaturated soils.