Abstract: To accurately study the influence of rock block shape on the shear mechanical properties of soil-rock mixture, proposed is a reverse reconstruction method of real rock block that can be realized only by camera and digital image processing technology, and established is a database consisting of 210 rock block models in 6 grain groups. Then, a fine modeling method of soil-rock mixture is proposed, and several different rock block sphericity models of soil-rock mixture are established, the numerical direct shear tests are carried out. The results show that: Most of rock blocks rotate along the shearing direction, resulting in an obvious "gear effect" and a "principal stress rotation"; With the increase of sphericity of rock block, the "gear failure" among rock blocks is more likely to occur, strong chains numbers and rotation angle are reduced, the thickness of the shear band becomes thinner, resulting in the reduction of the shear expansion, shear strength, internal friction angle and cohesion of the soil-rock mixture, among which the internal friction angle shows a linear decrease trend, and the cohesion decreases exponentially; In the backfill engineering, it is preferable to use the soil-rock mixture with low sphericity rock blocks.