Acoustic emission (AE) technique was utilized for real-time monitoring the damage evolutions of 2-D and 3-D C/SiC ceramic matrix composites (CMC) under mechanical loading. AE signals for damage initiation and propagation were captured by AE equipment during the entire loading process. Different damage mechanisms of the two kinds of C/SiC composites were revealed on the basis of multi-parameter analysis. The experimental results validate the availability of AE technique on damage monitoring of C/SiC composites. And the AE technique can be used to distinguish the slight differences in damage mechanisms during damage evolution owing to different woven structures.