Empirical formula of Duncan E-μ、E-B model can not simultaneously reflect the low confining pressure dilatancy deformation and high confining pressure shear contraction deformation in coarse-grained materials tri-axial shear test, and generalized hooke’s law, on which Duncan E-μ, E-B model is based, are not able to reflect the dilatancy characteristics of soils, so a new elasto plasticity constitutive model based on Shen Zhu-jiang’s double-yield surface theory is built by means of combining the volumetric strain laws presented by writer and Shen Zhu-jiang’s double-yield surface theory. This model can well reflect the soil dilatancy characteristic, accurately fit equal confining pressure shear test results, and can predict the test results of equal stress ratio path, equal average principal stress path, equal large principal stress, minor principal stress reduction path, equal minor principal stress and shear stress reduction path and so on.