Abstract: The migration and blockage of fine particles in coarse-grained soil under the action of seepage in muddy water is of great significance for improving the performance of artificial infiltration facilities and preventing internal erosion of water conservancy projects. Therefore, a self-made seepage device was used to carry out the seepage test of muddy water in coarse-grained soil.? The influence of fine particle content in muddy water on its permeability characteristics was analyzed. The relative porosity of coarse-grained soil, the permeability coefficient of each medium layer and the relationship between the overall permeability coefficient and the siltation layer were discussed, and the theoretical formula was compared with the test results. The results show that under the geometric and hydraulic conditions, controlling the particle size d0.075 is an important factor affecting the deposition of fine particles in muddy water on the surface of coarse-grained soil, and its deposition rate conforms to Boltzmann function. The control particle size content d0.075 in muddy water can be used to describe the clogging form of fine particles to coarse-grained soil. When d0.075 ≤ 20 %, it is the surface accumulation clogging form (S form) ; when 20 % < d0.075 ≤ 60 %, it is the surface-internal double clogging form (S-I form) ; when 60 % < d0.075 ≤ 80 %, it is the internal pore clogging form (I form) ; when 80 % < d0.075, it is the transient pore clogging form (P form). The permeability coefficient of each medium layer of coarse-grained soil column under four kinds of clogging forms is different, especially in the S-I and I forms, the permeability coefficient of the lower part of the soil column decreases significantly lagging behind the upper part, and the permeability coefficient of the top of the four clogging forms is the smallest ; the overall permeability coefficient of the coarse-grained soil column gradually decreases with the increase of the thickness of the deposition layer. The overall relative porosity of the coarse-grained soil column decreases first and then increases with the increase of the control particle size content. There is a critical control particle size. When it is about 60%, the overall relative porosity reaches the minimum value. In addition, as the water head is higher and the non-uniformity coefficient is smaller, it will aggravate the migration and deposition of fine particles in muddy water, resulting in a smaller overall relative porosity. The relative porosity of each medium layer of coarse-grained soil column is different in four forms. It is worth noting that there is a critical depth of 4~6cm in S-I and I form, and the relative porosity of this layer is basically unchanged. This study provides a theoretical reference for the blockage of muddy water seepage in other porous media, and also provides technical means for engineering application.