Abstract: A micromechanical model was developed for predicting effective hygrothermoelastic properties of composites and local field distributions within the unit cell based on the framework of the variational asymptotic homogenization theory. Starting from the derivation of the hygrothermoelastic free energy functional of composites, the leading variable item in the functional of free energy was asymptotically analyzed by taking advantage of the small ratio of microscale to macroscale. Micromechanical model and the recovery relationships of local field distributions for the hygrothermoelastic problem were obtained and implemented by using finite element method. Comparison with ABAQUS finite element example shows the constructed micromechanical model can predict the effective hygrothermoelastic properties of composites and local field distributions effectively and accurately.