<p>The existence of defects will inevitably affect the mechanical behavior and failure characteristics of the backfill, ultimately degrading its stability and accelerating the progression of damage. To this end, uniaxial compression experiments were conducted on prefabricated flaw cemented tailings backfill (PFCTB) containing different defect angles, and the failure process was detected simultaneously using acoustic emission (AE) equipment and digital image correlation technology (DIC), with a focus on the influence of prefabricated flaw angles on the mechanical behavior and cracking characteristics of cemented tailings backfill. The results show that: (1) The peak strength and elastic modulus of the cemented tailings backfill appeared to decrease, followed by an increase from 0° to 90° of prefabricated flaw angles, with the smallest values of peak strength and elastic modulus at a prefabricated flaw angle of 30°. (2) When the flaw angles were 0°, 45°, and 60°, the specimens predominantly exhibited tensile failure, with tensile crack proportions of 94.3, 88.1, and 79.1%, respectively. Meanwhile, at flaws angles of 30° and 90°, shear failure dominated, with shear crack proportions of 58.2% and 64.9%, respectively. (3) The proportion of AE signals in stage III and stage IV is the highest, where a large number of cracks and crack penetrations occur, which are important causes of overall failure of the specimen. The process of crack evolution and damage in PFCTB specimens can be synergistically reflected by the b-value of the AE parameter and the strain and stress of the DIC, which can effectively predict the failure of PFCTB specimens in terms of instability. These results provide a basis for the stability evaluation and strength design of cemented tailings backfill with defects.</p>