Al 2 TiO 5 flexible ceramics (AT-FCs) are attractive material with nonlinear stress-strain behavior due to their multi-cracks structure. [1,2] The application of AT-FC to prepare shockproof component especially in high temperature has emerged as a new and viable choice. Although researches toward enhancing the study of AT-FC have been going on for more than 10 years, the damage-mode evolution inside still remains elusive. [3][4][5] Using nondestructive techniques will increase the confidence of both engineers and researchers in the full utilization of the potential of this material. Acoustic emission (AE) is widely used in real-time monitoring the damage process in materials. [6][7][8][9][10][11][12][13][14][15] Generally, the gathered AE data will be saved as the signal parameters such as energy, count, rise time, duration, and amplitude. These key parameters can be utilized directly or as a derived combinations. [11] In AT-FC, the possible AE single source mainly results from the fracture of grain boundary glass phase, friction between grains, and grains failure. [16] Meanwhile, a single-damage mode, such as fracture of grain boundary glass phase, can provide multiple AE signal parameters. In addition, the overlapping of AE parameters distribution area is ineluctable due to the equipment settings, dense AE from various signal sources, and signal fading. [11,17] Therefore, the relationship between each damage mode of AT-FC and AE signal parameters has not been built. However, to achieve damage-mode automatic identification of AT-FC, it is necessary to build this relationship in advance. Machine learning (ML) is a suitable method for accomplishing the corresponding relationship between each damage mode of AT-FC and AE signal parameters to realize automatic identification of damage mode. The ML algorithms contain two modes, unsupervised and supervised. [18] The target of unsupervised ML is to classify the AE parameters with similar characteristics into groups and utilize those groups to distinguish different damage modes, while supervised ML is used to identify the damage modes of other materials in the same set using the distinguished damage modes.Generally, the AE signals handled by ML algorithms have been concentrated on the mechanical properties analysis of fiber-reinforced ceramic/glass matrix composites. Moevus et al. [19] employed the unsupervised ML algorithms, k-means, to explore the damage modes of two kinds of SiC f /[Si-B-C] composites. Five and four damage modes were accurately distinguished in elongation composites and stiff composites, respectively. Meanwhile, Kostopoulos et al. [13] successfully identified three damage modes in SiC/mixed abrasive slurry-L (ceramic glass matrix) composites utilizing k-means algorithms. However, it is necessary to combine the unsupervised ML algorithms with supervised ML algorithms to achieve the automatic identification