Abstract: Natural frequency characteristics and damage evolution of woven SiC/SiC composites were investigated under cyclic loading-unloading test at room temperature. The results show that the natural frequency decreases with the increase of peak stress during the runs, then the natural frequency and elastic modulus reduction degree of the composites were determined by defining the frequency decay parameter Φ and the modulus decay parameter D, respectively. Based on the micromechanics theory, the cyclic loading and unloading hysteresis loops of woven ceramic matrix composites were calculated theoretically, and the simulation results are in good agreement with the experimental data. Besides, the analysis reveals that the modulus decay parameter D, the interfacial debonding ratio 2l_d/l_c, and the fiber fracture probability q all exhibite an obvious upward trend with the increased frequency decay parameter Φ. Matrix cracking and interfacial debonding took place when the natural frequency of composites declined by 1%. Moreover, when the natural frequency decreased by 4.17%, the interfacial debonding ratio was increased to 1 (that is fully debonding), and the fiber fracture probability was increased to 2.5%, which indicates that the variation of natural frequency can effectively reflect the internal damage and invalidation process of the material.