Abstract: The damage characteristics of the acoustic emission signals produced in high temperature ceramic matrix composites were analyzed based on the relations between acoustic emission (AE) signals and X-ray CT images. The characteristic parameters including the frequencies of AE signals were obtained by analyzing the signals of macroscopic stress waves in the case of composite damage by using AE technology. Existing damage types can be confirmed by the microscopic 3D damage images of composite structures were obtained by CT method. The results showed that different types of damage can generate in the interior of ceramic matrix composite specimens fabricated by different processing techniques under tension load. The corresponding frequency of AE signals for the delaminations between fiber bundles and the matrix damage and fiber bundle fracture were respectively 44 kHz, 150 kHz and 250 kHz.