Based on the ultra structure properties of bone, the constitutive relation of lamellae bone and theultra structural model of osteon were provided with the method in the mechanics of composites. Theaxisymmetry strain problem of the osteon was solved. This model shows that the elastic coefficientsof conical bone are not only the function of bone porosity, but also the functions of the content ofcollagen and mineral and the orientation of collagen fibres.