Abstract: Both the undisturbed soil and remolded soil have initial structural properties, and the shear stress resisted by the initial structure of the soil is the structural strength of the soil. In order to study the initial structural strength of the uncemented coarse-grained soil, this paper defines the characteristics of the initial structural change points of the coarse-grained soil during the shearing process, and divides the coarse-grained soil into four structural types according to the content of the coarse-grained soils greater than 20 mm. Visual direct shear instrument direct shear tests are carried out on the coarse-grained soils with different structural characteristics, and the critical strength of the coarse-grained soils with different initial structures is determined through the numerical value and the change trend of the initial structure indexes of the coarse-grained soils during the shearing process. The results show that the shear strength of the coarse-grained soils with different initial structure types under the same normal stress and the same particle type are in the same order as the proportion of the structural strength, indicating that the particle structure strength plays a role in the whole process of the resisting shear stress. The average structural strength of the four initial structure types of the coarse-grained soils accountes for 36.27%, that is, the structural strength accountes for 36.27% of the peak shear strength. The arranged contact structure has the highest structural strength at 36.62%, followed by the mosaic structure 36.61%. The suspended dense structure is 35.99%, and the superimposed structure has the lowest proportion of the structural strength, which is 35.87%.