A three dimensional(3D) generation procedure for randomly created irregular polyhedron coarse aggregates was developed, and a 3D discrete element(DE) model of asphalt mixture(composed of coarse aggregates, asphalt mastic and air voids) specimen in rutting test was reconstructed. The two dimensional(2D) DE model of asphalt mixture specimen in rutting test was constructed by cutting numerically the 3D DE model. The corresponding micro contact models and parameters were given for the interactions of microscale components of 2D DE model of asphalt mixture specimen in rutting test. The rutting test of asphalt mixture was simulated using the 2D DE model. Finally, the translation and rotation of coarse aggregates during permanent deformation of asphalt mixture were analyzed. It is found that the 2D DE model can more accurately describe the space movement of coarse aggregates during permanent deformation of asphalt mixture, and provide a new research method for investigating the rutting mechanism of asphalt mixture.