Enhancing rainwater infiltration is important to reduce the risk of urban waterlogging and improve the utilization rate of urban rainwater resources. Using the HYDRUS model, a mathematical model of soil water movement under a banded sand ditch pattern (the vertical excavation of a deep trench with heavy soil and filled with light soil) was created. Forty-six scenarios were designed to examine effects of sand ditch soil saturated hydraulic conductivity (Kss), original homogenous fine-textured soil saturated hydraulic conductivity (Kso), sand ditch width (W), spacing (S), and depth (D) on the soil infiltration rate (i). Results indicate that banded sand ditches cause increased permeation and have a significant turning point 't0' in the curve of 'i' for 't.' Taking 't0' as the boundary, 'i' can be divided into two stages (t ≤ t0 and t > t0), 'i' and 't,' for each stage according to the power function relationship; there is little change in power function indices, which can be fixed at 0.34 and 0.63, respectively. In addition, the coefficient has a linear relationship with Kss, Kso, W, S, and D. Thus, an estimation model of the soil infiltration rate under a banded sand ditch pattern was proposed and verified for reliability.