Abstract: To accurately predict the typical thermoelastoplastic behavior and initial yield surface of metal matrix composites (MMCs) with periodic microstructures, a micromechanical model and corresponding increment equation were presented based on the variational asymptotic method. This model uses the characteristic of small ratio of micro scale to macro scale to asymptotic expand the unit-cell variational energy functional changes. The effective instantaneous elastoplastic stiffness matrix and thermal stress matrix were calculated. The iterative homogenization and localization technology were used to simulate the nonlinear thermoelastoplastic performance of MMCs. The corresponding calculation model was realized through finite element technology. The numerical example analysis shows that this model can well predict the initial yield surface of MMCs and simulate thermoelastoplastic coupling behavior, which can provide technical support for further study and practical application of MMCs.