This paper presents a double-structure elastoplastic constitutive model that can describe the hydromechanical behavior of compacted bentonite. The model is formulated based on a new developed double-structure hydromechanical framework that consists of four key components, including the mechanical model and water retention model at the macrostructure scale and microstructure scale, respectively. Hydromechanical coupling at each structure scale is achieved by liking the effective stress with the corresponding water retention model. Independent coupled hydromechanical models are developed for each structure scale and the global response is obtained with an introduction of the structure parameter ξ. The elastoplastic deformation occurs at both the microstructure and macrostructure in the proposed model. Model responses under the different hydromechanical loading paths are finally discussed and the model performance is investigated and validated via simulations of comprehensive tests on FEBEX bentonite. The simulation results demonstrate that the proposed model is able to reproduce various swelling behavior of compacted bentonite, including the swelling deformation under different constant stresses and the swelling pressure under the constant volume. In particular, the dry density effects can also be reproduced.