An improved three-cell model,which includes warp-weft cell,warp tying cell and contact cell,is proposed based on the geometry characteristics of the yarns for 3D orthogonal woven composite. The deformation and structural characteristics of yarns in cells are considered. The cross-section of yarns,especially extrusion yarns,is equivalently deal with so that the present model is common and the corresponding calculation is simple. The effective elastic properties of cells are obtained by using the homogenization method. Then based on the stiffness volume average method,the elastic stiffness of 3D orthogonal woven composite is calculated. Comparing with the available experimental data,the result of numerical example shows the present model is effective and reasonable. Also,the effect of the woven angle on the elastic stiffness of 3D orthogonal woven composite is discussed,i. e.,the increase of the woven angle leads to the increase of the transverse modulus and the decrease of the longitudinal modulus.