The thermal residual stress of C/SiC affects the service performance of the material. In order to explore the influence of initial defects on the thermal residual stress, the steady change temperature method and the finite element computational mechanics (FECM) method are used to determine the relationship with thermal residual stress and initial defects of plain weave C/SiC composites. The distribution characteristics of various initial defects of the material were measured and statistically analyzed by scanning electron microscopy (SEM) of the sample. The representative volume unit (RVE) and the fiber bundle RVE finite element model of the macroscopic material with initial defects were established to predict effective performance parameters and thermal residual stress of fiber bundle RVE, and obtain the quantitative relationship between various initial defects and thermal residual stress of macroscopic materials.