To solve damage issues of asphalt overlay resurfacing old cement pavement, authors put forward ideas of interlayer water breakage, expounded the mechanism of dynamic water pressure, designed a kind of composite specimens, and separately finished the direct shear tests with the samples water immersion and freeze-thaw for the first time in China. Based on the model of water-tire-pavement system, it is concluded that dynamic water pressure rises with vehicle speed, directly 2 power proportional to speed, and the dynamic pressure were identified as 0.25MPa, 0.40MPa, 0.55MPa corresponding to the running speed of 80km/h, 100km/h, 120km/h, respectively. According to direct shear tests with soaked samples, the longer the sample soaked, the more is layer structure vulnerable to damage. Compared with the sample not-soaked, the shear strength respectively reduces by 50% or 64.6%, corresponding to the samples soaked 24h or 48h. With the freezing and thawing sample, direct shear tests show that the roles of the hydrostatic water in layer leads to interlayer structure intension lessening by 58.8% over the natural sample. The results declare that the bond is weakened by dynamic pressure, soaking, freezing and thawing of interlayer water, which will eventually result in overlay structure destroyed.