Surface free energy theory, attenuated total reflection infrared spectroscopy(FTIR ATR) and atomic force microscopy(AFM) were used to study the asphalt under water erosion from macroscopic and microscopic perspectives. The mechanism of adhesion attenuation at the asphalt aggregate interface was studied and the effect of aging on the decay process was investigated. The results show that the water content in the asphalt increases with the prolongation of the immersion time when the peak area of hydroxyl stretching vibration is used as an index. After the aging of asphalt, the diffusion rate of water in asphalt is accelerated, which makes water more easily diffuse to the asphalt aggregate interface, and has more significant influence on the diffusion coefficient in the first diffusion stage. The aging of asphalt reduces the adhesion at the asphalt aggregate interface, and in the presence of water, the asphalt film is more inclined to be replaced by water from the surface of the aggregate, thereby causing spalling; the microstructure changes of bitumen with different oil sources after immersion are very similar, indicating that the mechanism of their interaction with water is the same.