Abstract: On the basis of microscopic observations, a reasonable 3D unit cell model of 3-dimensional (3D) five- directional braided composites was established. The yarn packing factor and the cross-section deformation due to the later compression, which were neglected in the existing model, were both considered in the model. Based on the unit cell model, the elastic modulus of the material was calculated by 3D finite element analysis ( FEA). The numerical results show good agreement with the experiment data. The stress field of the model under tensile load was analyzed, which provides a basis for farther strength prediction.