Abstract: Acoustic Emission (AE) signals of 2D-C/SiC ceramic matrix composites under monotonic tensile test and cyclic tensile test at room temperature were studied. The unsupervised hierarchical clustering method was used to identify the damage pattern of AE signals in monotonic and cyclic tensile tests. The stress and acoustic emission signals of each monotonic loading/unloading test were analyzed respectively, and the damage conditions of the samples in the cyclic loading interval and the unloading interval were obtained. By comparing and analyzing the AE signals of the two tensile tests, it is found that when the same stress is first loaded in two tests, the two samples have the same type of AE damage signals, which indicates that the repeated loading has little impact on the main damage of the samples.