Abstract: A unit cell model is established on the pattern of the rule of the yarn movement and the relationshipbetween the braiding parameters is deduced. Based on this model , the elastic properties of three-dimensional six-directional (3D & 6D) braided composites were derived with the method of stiffness averaging and the influence of thebraiding angle adn the fiber volume f raction was analyzed. The result s show that the 3D & 6D braided composite hasgood mechanical properties and it s in2plane mechanical performance is improved by joining the in2plane t ransverseyarns.