Abstract：Acoustic emission(AE) and its location technique are utilized to study the failure process of different sized rock samples under different loading conditions(uniaxial loading，Brazilian splitting testing and three-point bending loading). From experimental results，the position of AE events corresponds to the position of stress concentration during the elastic loading step. With the increase of external loading，AE instrument can exactly locate the position of crack initiation and propagation；and AE location events can reflect the stable crack propagation process. The AE location result of Brazilian splitting testing indicates that，the position of initial crack is generated randomly，and the initial crack is the primary factor inducing rock instability. The failure modes of rock samples are varied by the sizes of granite samples. The AE activity is influenced by crack generation during loading process；by contrast，the AE activity is different for various rock samples as well. The AE activity of granite sample shows stress jump，but few AE events are generated during initial loading processing and elastic loading period of sandstone. The AE events increase abruptly with the external loading，which is related to the characteristics of rock components. AE location results also directly reflect the spatial position，direction and spatial curved face of crack propagation in the rock samples，which provides very significant evidences for the study of rock failure mechanism.
