Abstract: Plain weave SiC/SiC composites were manufactured by the chemical vapor infiltration process，and X-ray computed tomography non-destructive testing technology was used to investigate the damage evolution and failure mechanism of textile ceramic matrix composites. Besides the third generation SiC fiber toughened plain weave laminated SiC/SiC dog bone test pieces were prepared. In addition, a CT in-situ tensile tester was developped, the nano in-situ X-ray CT tensile tests were completed, and the three-dimensional reconstruction images and scanning electron microscope photos of CT scans were analyzed. The results show that nano X-ray CT in-situ tests can reveal the evolution of tensile damage of materials. The uniaxial tensile stress-strain curve of plain weave SiC/SiC composites exhibits obvious nonlinear characteristics, with damage initiating in the stage of nonlinear changes. First, lateral cracking of the substrate occurs and gradually expands with increasing tensile force. Next, interlayer matrix cracking and fiber bundle matrix cracking occur longitudinally and gradually expand to the fiber bundle width. Finally, the fiber in the tensile direction breaks and the material fails. Most of the substrates have transverse cracks closed, but the longitudinal fiber bundles and the matrix between the bundles are severely separated, the fractures are uneven, and there are obvious fiber pull-outs.