Abstract: According to the characteristics of large particle size of soybean, the corresponding microscopic parameters of soybean were calibrated on the basis of soybean direct shear test. The numerical model of large soybean direct shear test was established by discrete element method. The shear rate, wall material and water content of the sample were set to three single variables, and the other parameters as invariants. The effects of three variables on mechanical parameters such as soybean shear strength were studied. The results showed that when the shear rate changes within a certain range, the shear strength peak and internal friction angle of soybean did not change significantly, but the internal cohesion increased from 6.12 kPa to 9.31 kPa; the material of the silo wall changed from smooth surface to concrete slab. During the process, the internal friction angle of soybean changed from 26.9° to 32.33°, and its shear peak strength also increased to some extent, but its internal cohesion remained relatively stable; the shear strength of soybean with different water content was different. When the water content of soybean increased from 12% to 21%, the internal friction angle of soybean increased from 26.9° to 32.50°, and the internal cohesive force increased from 6.12 kPa to 11.01 kPa.