Abstract: A new micromechanics model was developed to accurately predict the effective thermal conductivity and local distribution of temperature field of heterogeneous composites using the variational asymptotic method for unit cell homogenization. Starting from a variational statement of the thermal conductivity problem of the heterogeneous continuum, the micromechanics model was formulated as a constrained minimization problem using the variational asymptotic method. The finite element method (FEM) was then used to solve the minimize solving process of energy functional with discrete form. To handle realistic microstructures in engineering applications, this new model was implemented using the FEM. The local fields within unit cell were recovered in terms of the macroscopic behavior including the global temperature and the corresponding gradient, and the fluctuation function. For validation, several binary composites examples were used to demonstrate the effectiveness and accuracy of the proposed theory.