Abstract: Taking silt soil image photographed by scanning electron microscope as the research object, using image treatment technology for microstructure observation and quantitative analysis of soil, the parameters of particle composition of soil were solved, such as porosity, grain diameter, granular shape, which provided physical parameters for setting up granular flow model.And then it was simulated the tri-axial test of the soil and studied the variation rules of property of silt soil with micro-parameters, such as friction coefficient, parallel-bond and stiffness ratio.The result showed that using clump model and particle repulsion method, the granular shape and grain diameter distribution could can be simulated.The model developed by this method fitted the stress-strain curves of soil and simulated the phenomenon of shear contraction and shear dilatation, the influence laws of friction coefficient, parallel-bond and stiffness ratio to the initial modulus and residual strength were different.The development process of shear zone could be reflected by monitoring the change of porosities.