Abstract: This paper introduces how the ratio R of the characteristic stiffness of rock sample vs. the. stiffness of testing machine would influence the rupturing process and the acoustic emission (AE) on the part of the tested rock samples. Result of the experiment shows: When R> 0.20, the rock sample would rupture abruptly, whereas when R1.50, no pre-failure quiescence is detected. When the rock samples rupture slowly, the variation pattern of the AE rate (after the stress has increased to more than 50% of the rupturing stress) is as the following: Stable low (or high) values-rising (or dropping) to its maximum (or minimum) values and then continuing for some time-rupturing.