To explore the fatigue damage mechanism and micro-mechanical behavior of the pavement of rubber powder asphalt mixture (ARHM- 20) of expressway influenced by heavy vehicles,a three-dimensional microstructural model of the mixture was built based on the discrete element method,and research on the damage mechanism from aggregate motion to macroscopic permanent deformation were conducted.The Burger's constitutive model was used to characterize the viscoelastic properties of asphalt mortar.The macro mechanical parameters of Burger ’s model at different temperatures were obtained through asphalt creep tests,and the micro modeling parameters were obtained based on the macro and micro conversion formulas.The irregular coarse aggregate was made by Solidworks software to make the model closer to the actual working conditions.In this paper,under the distributed loading method,the contact force was extracted after rolling the tire on the ground,and then the force was applied to the model.Based on the actual highway engineering gradation,the rutting test specimen was prepared and the laboratory rutting test was carried out to verify the validity and correctness of the three-dimensi onal microstructure model.The research results show that the discrete element method can be used to study the micro motion-mechanical behavior of asphalt mixture.The macro behavior of rutting evolution is mainly generated by the micro stress distribution and motion evolution of the coarse aggregate in the asphalt mixture.Compared with the asphalt mixture without rubber powder,the ARHM- 20 asphalt mixture has better high-temperature fatigue resistance.