A three-dimensional finite element model with different stitching diameter was established based on carbon fabric with 8/5 warp satin weave. The elastic modulus of the composites was predicted by the total damage and partial damage. The thicker stitch thread make the tensile modulus of the composites decrease, and the thinner stitch thread had little effect on the internal elastic modulus.Compared with unstitching,modulus variation of the different diameter is within 9.6%.The elastic modulus of the composites was verified.The results show that the experimental results were larger than the finite element prediction, and the experimental result agrees with prediction.