In order to deeply understand the mixture skeleton structure and thus provide a theoretical basis for the design of the asphalt mixture of dense skeleton，the discrete element method is employed to investigate the constitution of the skeleton and the main skeleton of asphalt mixture，the basic characteristics of skeleton microstructure and the stress transfer performance of skeleton． The results indicate that ( 1) the evaluation of the asphalt mixture skeleton quality lies in the stress transfer magnitude of skeleton and its ability to resist external loads; ( 2) the contact points in the mixture can be divided into valid contact points and invalid contact points，and the main skeleton is made up of coarse aggregates which are in contact with one another and are of a particle size of greater than 2． 36 mm; ( 3) the stress transferred by the SMA ( Stone Mastic Asphalt) mixture skeleton accounts for about 70%～ 80% of the loading stress; ( 4) the proportion of the stress transferred by the skeleton is proportional to the nominal maximum size of the aggregates，but it is inversely proportional to the thickness of the specimen; and ( 5) the contribution rate of the main skeleton to the skeleton stress transfer is more than 70% ．