Abstract: The finite element modeling method of random void defects in C/C-SiC satin weave composites and their influence on tensile mechanical properties were studied. Based on the microstructure of C/C-SiC satin weave composites and the micro morphology observed by experiments, the random distribution characteristic of the void defects was concluded. A three-dimensional random collision algorithm was proposed to reconstruct the void distribution in the composite, and a finite element model of the C/C-SiC satin weave composite with random void defects was established. The finite element analysis software ABAQUS was used to simulate the mechanical behavior of the material under tensile load, and the influence of the size and distribution form of the void defects on the tensile mechanical properties was discussed. The uniaxial tensile test of the sample was carried out to verify the effectiveness of the numerical simulation. The results show that the finite element model established by this method is consistent with the real microstructure of C/C-SiC satin weave composites with void defects, and the corresponding numerical simulation results are also in good agreement with the test data. This paper provides an effective method for the mechanical analysis and optimal design of satin weave composites with void defects and other composites with similar structural characteristics.