Abstract: The effect of diagonal arrangement of yarns on the structure of the five-axial three-dimensional((3-D)) woven fabric and the density of yarns in Z direction were analyzed,and two kinds of five-axial 3_D fabric structure were obtained. One was in loose structure with low density of the yarns in Z direction and the other was in compact structure having high density of the yarns in Z direction.Based on the compact five-axial(3-D) fabric,this paper constructed the unit_cell model for the five-axial 3_D fabric.Using analytic geometrical method, the cross-section of the yarns in Z direction was calculated.According to the relationships between W_β/W_X,W_β/W_Y with cos β,sin β,it was found that the cross-section shapes of the yarns in Z direction can be octagon,hexagon or quadrilateral.