The shear deformation characteristics of soft clay are important factors determining the safe existence of marine structures and pipelines, and discrete elements method can effectively simulate clay properties. Through the consolidated-undrained (CU) triaxial testing, we can obtain the shear strength parameters and other parameters required for discrete element simulation. A set of meso-parametric combinations suitable for soft clay in the South China Sea was calibrated by trial and error method. The results of biaxial compression simulation were consistent with laboratory tests. The discrete element simulation results show that when the strain reaches 5.3%, the soil damage and a shear zone with a negative X direction of 49° is formed. As the strain increases, the shear zone inclination angle increases. A small angle of deflection occurs in the main dominant direction of the contact normal direction, the normal contact force, and the tangential contact force during the shearing process. By setting the measuring circle to monitor the strain inside and outside the shear band, the initial strain of the soil in the shear band is large, and the deformation does not continue after reaching 4% strain and the soil strain continues to increase in the edge region of the shear band. The strain outside shear band is small. The general laboratory triaxial test can not obtain quantitative data of soil strain changes inside and outside the shear band, so the discrete element method is an effective supplement to the laboratory triaxial test.