Abstract: Considering the structure characteristics of 3D orthogonal woven composite (3D-OWC)，a cell model composed of three orthogonal bundles of fibers and matrix was proposed based on the assumption that the fiber bundle has the rectangular cross section. According to the cell model，an equation relating the fiber volume fraction and the woven parameters (such as the fiber roughness，weaving density and so on) was obtained. The relatively simple formulas of Young‘s modulus of 3D-OWC were developed by the assumption that both the fiber and matrix are elastic. With the new formulas，three dimensional orthogonal composite’s Young's modulus can be got by the fiber modulus，matrix modulus and fiber volume fraction. The fiber volume fraction and elastic modulus calculated by the equations are in good agreement with the experiments. It is concluded that the proposed cell model is effective and valuable，and it will be useful in the study of 3D-OWC mechanical properties.