The interface transition zone（ITZ） of two types of asphalt mixture were studied by the nanoindentation test. The mechanical properties of ITZ were evaluated based on the fracture toughness. The results show that the thickness of the ITZ of asphalt mixture with basalt aggregate ranges from 6 to 12 μm， while the thickness of the ITZ of asphalt mixture with limestone aggregate ranges from 10 to 18 μm. The mechanical properties of the ITZ are close to those of the aggregates. The anti-cracking performance and stability of ITZ are jointly affected by asphalt and aggregates. The resistance of asphalt to cracking is improved with an increase in fracture toughness， and cracks are more likely to occur at the junction of ITZ and asphalt mastic， especially asphalt mixtures are more prone to brittle fracture at the interface between ITZ and asphalt mastic.