Abstract: Internal erosion is one of the main causes of seepage damage in natural sediments or geotechnical structures. In the seepage process, particle shape is an important factor affecting the development of erosion in soil. At present, the experimental research on the internal erosion of soil seepage is limited by real soil and conventional permeameters. The research on the mechanism and influencing factors of internal erosion is still insufficient, and the experimental research on the effect of particle shape on the internal erosion of soil seepage is even more limited. Focusing on the above key issues, this paper uses the transparent soil seepage internal erosion test device developed based on the complex shape particle generation algorithm, 3D printing technology and transparent soil technology to carry out the seepage internal erosion test of discontinuous graded soil with different particle shapes. The influence of particle shape on the development of internal erosion in discontinuous graded soil is explored, and the mesoscopic mechanism of the erosion development process in soil with different particle shapes is revealed. The experimental results show that particle shape is an important factor in determining the characteristics of internal erosion. The samples composed of elongated particles with low average aspect ratio (AR) have higher fine-grain erosion rate and faster erosion rate during seepage compared with spherical particles; while the samples composed of angular particles with high shape parameter d_2-8 values have smaller fine-grain erosion rate and erosion rate. The smaller fine-grain erosion rate also leads to a decrease in the permeability coefficient growth rate. In addition, the internal mesoscopic map of transparent soil reveals that the difference in pore throat structure between coarse particle skeletons is the fundamental reason for the distince development of internal erosion under different particle shapes.