[Abstract] The pore structure of soil is an important physical and mechanical index, which is of great significance for studying the deformation and destruction of soil. In this study, the pore structure, pore size and distribution of coastal soft soil were studied by laboratory test (SEM, CT technique) and numerical simulation (ArcGIS). The two-dimensional and three-dimensional pore structure of soil under hierarchical load were discussed. The three-dimensional porosity of ArcGIS based on CT test, the SEM two-dimensional porosity of PCAS statistics, 3D porosity calculated using SEM two-dimensional image, and the measured porosity of mercury intrusion test were compared to analyze the accuracy of different methods for determining porosity. At the same time, the SEM image was measured and analyzed, and the variation of the number of pores with different pore sizes with the load was statistically analyzed to analyze the consolidation mechanism and micro-macro-mechanical properties of the soft soil. The research shows that with the increase of vertical load, the large pores of the soil are gradually compressed, the average diameter of the pores is gradually reduced, the total pore volume is reduced, the structural units become tight, and the apparent porosity decreases. The axial, radial and volumetric shrinkage of the soil is caused by the compression of the pores and the deformation of the particles. At the same time, the fractal dimension of the pores is greatly affected by the compression of the pores and the particles, and the pores are determined by the perimeter-area method. The fractal dimension is affected by the threshold selection, but the volume-area method is not affected by the threshold selection.