A seepage slope stability analysis model for an ancient city wall for flood protection in Lanxi was constructed based on the finite element software ABAQUS. A seepage-stress coupling calculation method was used to simulate the variation process of pore water pressure in the soil behind the ancient city wall under the condition of rainfall infiltration, and the seepage and deformation characteristics of the ancient city wall with anti-seepage facilities, drainage facilities and no drainage facilities were compared and analyzed.The study results show that under the condition of rainfall infiltration, the pore water pressure and overturning moment of the soil slope of the ancient city wall with anti-seepage facilities or no drainage facilities can be increased, which is not conducive to the stability of the ancient city wall. The pore water pressure of the soil slope inside the ancient city wall with drainage facilities is greatly decreased through the drainage channel, and the overturning moment is also reduced, which is more conducive to the stability of the ancient city wall.