A new dynamic performance degradation testing platform of advanced composite structures under high temperature-scouring-vibration environments has been self-designed and developed to achieve corresponding tests under such coupled environments. Firstly, the functional design and implementation principles of various parts of this system were introduced in detail, and the construction of the testing platform was completed. Additionally, the degradation curves of natural frequency and resonant response of quartz fiber ceramic matrix composite thin plates under various temperatures, degradation time, and flushing time were obtained based on the above testing platform. The results indicate that the effects of high temperature, scouring, and vibration lead to the degradation of the dynamic performance of ceramic matrix composites, characterized by a reduction in the first two natural frequencies and a significant amplification of the resonant response.