Abstract: Thermal protection structures (TPS) are key structures for reusable space vehicles, whose safety and maintainability are of vital importance. There are very few researches on structural health monitoring for TPS, especially for C/C, C/SiC composite TPS. The structural health monitoring method based on active elastic wave was studied for the C/C TPS of reusable space vehicles. A numerical simulation method of TPS elastic wave was proposed. On the basis of verifying the effectiveness of the method, the elastic wave propagation characteristics for C/C TPS structural damage monitoring were studied. From signal time domain characteristics, elastic wave propagation wave field, damage scattering signal, damage scattering signal wave field and damage index, analyzing the elastic wave propagation characteristics of C/C TPS and the effects of damage were analyzed completely. The results show that when the length of the stratified damage edge is greater than 25 mm, the damage index changes dramatically, so the structural health monitoring method based on elastic wave can be used to monitor the internal stratified damage and damage expansion of C/C TPS.