Abstract: One of the aims in the design of 3D fabric parameters is to meet the requirement of fiber volume fraction (FVF). By analyzing the unit cell of 3D orthogonal woven fabric, the sizes of warp, fill and binder yarn cross-sections were calculated and the relationships of FVF with the fabric parameters were established. The results could be used to theoretically calculate warp, fill and binder yarns', as well as the fabric's, FVF. A piece of glass fiber orthogonal woven fabric with 6 layer warp yarns and 5 layer fill yarns was manufactured to test the FVF and the calculated values were compared with the tested ones. The reasons that caused the difference between the theoretical values and the experimental values were analyzed. The factors, such as the ratio of warp thickness to fill thickness (Texw/Texf), the ratio of fill yarn density to warp yarn density (d_W/d_F) and the binder thickness, all of which affect FVF, were discussed. It was found that along with the increase of Texw/Texf or the decrease of d_W/d_F, the FVF of warp and fabric would increase, but the FVF in the fill direction would decrease, and the thicker the binder yarn, the smaller would be the warp, fill and fabric's fiber volume fractions.