Abstract: Based on modified classical laminated theory, the mechanical properties of three dimensionally braided composite materials were analyzed in this paper. Carrying out the integration and averaging of compliances yields, the effective elastic modulus of braided structural composites was predicted. Tsai Wu polynomial criterion was adopted and the strengths of 3 D braided composites were obtained. In addition, the mechanical experiments of braided structural composite materials were carried out. The effects of textile process parameters, such as braider angle, transverse angle, ratio of axial yarns number to braider yarns number and fiber volume fraction on mechanical properties were investigated. A comparison between theoretical and experimental results shows that the mechanical model can reasonably predict the stiffness and strength of 3 D braided composite materials.