Inorder to explore the influence of different particle gradations in muddy water on the infiltration law and formation characteristics of tight layer, indoor vertical infiltration experiments of soil pillars were conducted. In this study, four types of sediment with different physical clay content (5.59%, 9.87%, 18.43% and 39.43%) were selected and the variation characteristics of the thickness of the falling silt layer, the wet front migration distance and the cumulative infiltration volume with the infiltration time were studied, and the gradation of soil particles in the falling silt layer and the different depths after the infiltration (0—1 cm, 1—2 cm) were measured. The results showed that the greater the content of physical clay in the muddy cement sand was, the greater the thickness of the falling silt layer was. At the same infiltration time, the migration distance of the wet front and the cumulativ e infiltration amount per unit area decreased with the increasing of the physical clay content. The variation of the falling silt layer thickness with time conformed to the power function relationship (R² > 0.9), and the fitting coefficient decreased with the increasing of the physical clay content, and the fitting parameter changed around 0.5. Under different physical clay contents, the particle composition of the silt layer was similar to that of infiltration sediment. The particle composition of soil at 2 cm infiltration depth was similar to that of the original soil. The content of fine particles <2 mm in the soil at 1 cm infiltration depth increased compared with the original soil. With the increasing of physical clay content, the contents of fine particles <2 mm increased by 4.29%, 4.92%, 7.96% and 16.30% in different treatments, respectively. The research results could provide a theoretical basis for further exploring the characteristics of dense layers formed by muddy water infiltration.