<p>Soil is a multi-scale granular material and has dramatic particulate and structural characteristics. Soil particles are divided into matrix and reinforcing particles to establish a multi-scale soil cell model according to the mechanical effect generated by the interaction between soil particles at various scales and the physical mechanism at different structural levels of soil. A multi-scale Mohr–Coulomb strength criterion (MCSC) that accounts for the particle size of soil is proposed by using the soil cell model. A series of soil cell samples are prepared to conduct consolidated and undrained tri-axial compression test to determine the model parameters. The yield locus of the multi-scale MCSC is drawn on the deviatoric plan based on the theoretical analysis and test results. Results show that the yield locus of the multi-scale MCSC is also hexagonal and expands with the decrease in the size of the reinforcing particle and the increase in the volume fraction of these particles. In this regard, the multi-scale MCSC can relate the microscopic physical details of soil to its macroscopic shear strength.</p>