Abstract: To investigate the characteristics about the displacement of residual oil by foams after water flooding under low-frequency wave excitation, a foam-facilitated oil displacement experiment under low-frequency wave excitation was performed based on the microscopic inhomogeneous model, and the mechanism and effect of foam-facilitated oil displacement reinforced by low-frequency wave were analyzed. The results show that the low-frequency wave improves the sweep coefficient and oil displacement effect of foam flooding by improving the foam stability, creating local pressure disturbance, and reducing the wall adsorption capability, and the microscopic oil displacement efficiency is increased by 6.78 % under the low-frequency wave excitation. Compared with single foam flooding, the way for the displacement of column residual oil by foams under low-frequency wave excitation is that foams gradually move along the pore wall to the other side of the pore to achieve the effective displacement of residual oil through layer stripping, a small amount of emulsification and stable transportation, which improves the speed of crude oil migration from the matrix wall and the pore throat. For the residual oil at the blind end, the low-frequency wave excitation increases the foam disturbance at the entrance to the blind end, changes the flow direction of foams at the blind end, and creates favorable conditions for the foam flow into the blind end; for the continuous flake residual oil, the low-frequency wave slows down the abrupt advance in the foam flooding process, and improves the sweep efficiency and displacement effect of foam flooding in the small pore space.