A self-developed large direct shear apparatus was used to carry out the silt-concrete interface and silt shear tests in the yellow flood area under different water content. Through comparative analysis, the shear mechanical properties of the silt-concrete interface and silt under different normal stresses and water content were studied. The results showed that the shear stress-shear displacement curves of the silt-concrete interface and the silt exhibit strain hardening characteristics.The shear shrinkage deformation of the silt direct shear test is significantly greater than the silt-concrete interface. Under the same normal stress and water content, the shear strength of the silt-concrete interface is greater than that of the silt. As the moisture content increases, the difference in the shear strength between the silt-concrete interface and the silt gradually decreases. When the silt is close to saturation, the strength of the two is basically the same. In addition, the shear displacement of the silt under direct shear failure is greater than that at the silt-concrete interface. The cohesive force of silt, the cohesive force and friction angle of the silt-concrete interface are approximately linearly decreasing with the increase of water content, and the internal friction angle of silt increases slowly and then accelerately decreases as the water content increases.