Abstract: The near-bottom high-concentration muddy water bodies of sea bottom sediments in the estuarine and coastal areas, resulting from violent disturbance triggered by strong wave action, can give rise to undersea turbidity current, which plays an important role in transporting pollutants and carbonaceous matters from offshore areas to abyssal sea and also serves as one of the important forces driving land-sea interaction. The fluidity of near-bottom high-concentration sandy layers varies with different sand contents and constituents. Based on shear rate-shear stress relationship, this study analyzed the rheological properties of silt and muddy water with different sand concentration. Combined with the rheological test results of muddy water with different powder and clay ratios and different contents made by predecessors, the silt muddy water is subdivided into Newtonian, transitional and Bingham fluids in the range of 100—1350 kg/m³ sediment concentration, and the changing limit diagram of rheological properties of silt-laden muddy water with silt and clay components is given, which provides a reference for the classification of fluid properties in the study of near-bottom high-concentration sediment-laden layer movement.