Abstract: The morphology of clay particles not only reflects the mineral composition of clay, but also is one of the important factors affecting its physical and mechanical properties. In order to study the effect of material composition on the micro-macro properties of clay, we use the discrete element method to simulate the triaxial compression of soft clay samples with different particle morphology. Firstly, based on the SEM image, the orientation angle and concave convexity of clay particles in natural state are counted. The sphericity and concave-convexity are introduced as the characteristic parameters of particle morphology. Secondly, we construct a clay particle model based on the structural features of clay minerals that we count at the first step. Finally, with triaxial test discrete element simulation method, we analyze the effect of soft clay particle morphology on its macroscopic mechanical and microscopic properties. The results show that the flaky particle sample has higher initial modulus than the spherical particle sample, and the shear strength is larger. The flaky particle sample even tends to be horizontally distributed with the loading. We divide the loading processes into two stages as the clay particle model showing different characteristics in each stage. At the initial stage of loading, the sphericity of particles has a significant effect on the initial elastic modulus, and the initial elastic modulus decreases with the increase of sphericity. At the later stage of loading, the effect of concave and convex degree of particles on shear strength index is gradually obvious, and the internal friction angle and cohesion of samples decrease with the increase of concave and convex degree. Microscopically, the shape of particles also has a great influence on the displacement and rotation of particles.