Abstract: The migration of fine particles and the change of pore structure within the soil under seepage conditions are the key factors inducing geologic hazards such as landslides and debris flows. The fine particle erosion law of inversely graded soils has been widely studied, while the response mechanism of fine particle migration and pore structure in normal-grained soils remains unclear. In this study, based on micro-CT scanning technology, we carry out seepage tests on soil columns with different particle size ratios (3.0~46.15) and hydraulic gradients (3.5, 5.0, 6.5), and reveal the migration and erosion of fine particles and the dynamic evolution of pore structure in the normally graded specimens. The results show that: (1) the fine particles migrate uniformly with the increase of hydraulic gradient, and with the change of particle size ratio and hydraulic gradient to form a significant clogging and loss area; (2) the average porosity of the sample decreases with the increase of hydraulic gradient, and under the same hydraulic gradient, the porosity decreases sharply along the height direction of the coarse-fine interface and shows a "single-peak" distribution, and the peak porosity decreases by 10% compared with the initial state at a particle size ratio of 17.33. The research results provide a more robust scientific basis for the prevention and control of seepage-induced soil instability.