The theoretical precise solution on predicting permanent deformation of asphalt pavements is proposed,which differs from those numerical solutions such as the finite-element methods,obtained by others.The Mohr-Coulomb criterion and the Mindlin's solution are used to determine the boundary between the elastic and plastic regions.The rigid-plastic assumption simplifies the 1-D Burgers model and thus simplifies the calculation of plastic deformation.Such simplified 1-D Burgers model is extended to 3-D case as the usual treatment like 3-D Hooke's law.Based on the above assumptions,the downward and upward plastic deformations of asphalt pavements have been calculated.The upward plastic deformation is nearly equal to 1/2 of the downward plastic deformation,such result nearly agrees with lot of engineering observation data shown in text book.