To address issues like seedling blockage and damage during the falling and clamping processes in the development of mechanized kelp seedling clamping equipment, this study measured the biomechanical parameters of suitable - period kelp seedlings (Saccharina japonica) to obtain the mechanical parameters and deformation patterns of their stems and leaves under external forces. The structural composition of kelp seedlings was introduced, and their biological characteristics were measured. A texture analyzer and a friction coefficient analyzer were used to measure the mechanical properties of kelp seedlings, and discrete element simulations using EDEM verified the compression characteristics of kelp seedlings. Results showed that the tensile strength of kelp seedling stems ranged from 0.67 to 0.79 MPa, their shear strength from 1.95 to 2.23 MPa, and their compression recovery from 0.43 to 0.46. For kelp seedling leaves, the tensile strength was between 0.52 and 0.71 MPa, the shear strength between 1.12 and 1.74 MPa, and the compression recovery between 0.03 and 0.06. The tensile and shear strengths of kelp stems and leaves decreased with increasing loading speed, while the compressive recovery increased. Among stainless steel, rubber, and silicone, the friction coefficient between kelp seedlings and silicone was the highest when the normal force and loading speed were constant. The error between the simulated and measured radial compression values of kelp seedling leaves using EDEM was 8.2%. These findings offer data and theoretical support for optimizing the design of kelp seedling clamping equipment.