Abstract: Based on the continuum damage theory, the stress-strain relationship for orthotropic materials with damage cracks was derived. A representative volume unit cell for 3D five-directional braided composites was constructed, in which the debonding on the interface was considered. The sizes of the finite element mesh and the crack were considered in the damage evolution equation. The Hashin and von-Mises criteria were used for prediction of the initial damage of yarns and matrix, and the Eshelby-Mori-Tanaka method was applied to calculate the stiffness reduction factor. The progressive damage behaviors were simulated by ANSYS, and the stress-strain curve and the critical strength under uniaxial tensile loading were obtained. It is shown that the main failure mode of the composites with a low braiding angle is yarn cracking with serious damage on the interface. The results from the simulation agree well with the experiments in the existing literature.