ASP flooding is an important approach to further increase recovery of a late stage high water cut oil field, but the damage to reservoir after ASP flooding cannot be neglected. In order to better investigate micropore changes, we have detected and analyzed in detail the pore structure changes and contact angle utilizing AFM (atomic force microscope) and optical contact angle meter through the micro pore experiment. The results show that: the wettability of reservoir rock turn to neutral wetting after the asp flooding, the combination of Ca2 +and anionic surfactant may make silica surface water to wet from oil wet transformation. Surfactant on the reservoir rock wetting role by stratigraphic water inorganic ions synergy effect.