Abstract: The silt is widely distributed in China and the occurrence of liquefaction is closely related to its microstructure. The macroscopic liquefaction characteristics and microstructural characteristics of the silt are combined to analyze the change of the microstructure of the silt with different clay contents. The microstructural images under different clay contents are obtained by the scanning electron microscope (SEM), and the Plus Image-Pro (IPP) image processing software is used to calculate and analyze the micro parameters of the silt. The results show that the interior structure of the silt becomes close with the gradually increasing clay content. The contact of particles transforms from the direct line or surface transformation into the point contact, and for the pore space types the overhead pore becomes the mosaic one. The pore area increases with the increase of its radius, and the number of micro, small and medium pores increases at first and decreases with the increase of clay particle content. The morphology of the micro, small and medium pores is essentially the same, but the abundance and fractal dimension of macropores increase significantly, and the complexity of the structure increases. Through change of the microstructure of the silt with different clay contents, the influences of clay content on its microstructure and micro mechanism of the macro liquefaction characteristics are revealed.