After the strong-alkali ASP system is injected into the reservoirs，the chemical reactions and physical changes take place between the alkali and mineral composition. The strong alkali dissolves the rock surface，and the dissolution products and clay particles migrate and precipitate on the flow channel of the reservoir，which causes great damage to the fluid flow. Taking Block A of Daqing Oilfield as a case，through percolation experiment by using the scanning electron microscope（SEM）and energy spectrum analysis，the damage mechanism of the strong alkali to formation and the change of mineral composition after dissolution are analyzed based on the dissolution of alkali to mineral composition，and then the influence on the core percolation ability is discussed. The core percolation experiment shows that the injection pressure increases about 140 kPa and the core permeability decreases about 18% after the long-term displacement using strong-alkali ASP system. Due to the dissolution caused by the strong alkali and percolation erosion，the original pore structure of the core is strongly destroyed，and the crystal structures of the kaolinite and montmorillonite etc. are destroyed also. After longtime displacement，the sediment formed after the alkali solution reaction and the clay particles detached migrate and stick to the surface of the pore throat channel，which causes the decrease of the core permeability. The results of SEM show that the surface characteristics of the rock minerals change before and after displacement，and the element content changes with the particle migration，which further verifies the effect of the strong-alkali ASP system on core permeability.