Abstract: There are often some branching strata in the foundation soils of engineering.Through grouping the branching strata in mechanical property,and considering the influence of branching strata to the constitutive relationship of integral foundation soils,the constitutive equation of foundation soils with branching strata is obtained,which offers a new thinking way to solve the constitutive relationship of foundation soils with branching strata.By using the theory stated above,the elastic parameters of transverse isotropic foundation soils can be obtained considering the varity of elastic parameter with depth.