Abstract: As the main component of the landslide accumulation layer, gravel soil is affected by hydrodynamic factors; the change of internal seepage pressure leads to the loss of soil particles, resulting in the change of meso structure and mechanical properties, and thus affecting the overall stability of the landslide. To analyze the evolution of the internal pore microstructure of the crushed soil during the seepage process, the indoor seepage erosion test was carried out on the crushed soil specimen by the self-designed seepage device, using CT scanning to obtain internal pore image data of the seepage erosion process of crushed stone soil samples. Through the identification of porosity and parameter extraction, the changes of mesoscopic parameters such as internal porosity and equivalent diameter of the specimen during the seepage process were analyzed. A pore network model was constructed to analyze the variation of pore radius, throat length, and coordination number of connected pores under different seepage conditions. The results show that the gradual increase of the hydraulic gradient will change the pore distribution in the internal soil. The soil particle erosion leads to the porosity increasing, the pore quantity increasing first and then decreasing, and the total pore volume increasing. Seepage will promote the pore expansion and penetration, and enhance the pore connectivity. The average pore throat radius and average coordination number increase with the hydraulic gradient increasing. This study can provide theoretical significance for the prevention and treatment of gravel soil landslides.