The corelation between acoustic emission characteristics and their fracture toughness has been investigated in this paper based on the study of high-strength al uminum alloy cracking process by using advanced acoustic emission experiment sys tem and smooth tensile specimens as well as DCB specimens with premade cracks. E xperimental results showed that the specimens emitted strong signals with an amp litude above 35 dB when a stable crack extension started at K1C. Stro nger and more complicated acoustic emission signals were found during unstable crack extension, and the cumulative energy of acoustic emission events were found to b e linearly related with the macroscopic fracture energy.