Abstract: Experimental studies on rock damage process based on acoustic emission (AE) technique were carried out under cyclic loading. On the basis of damage theory and load/unload response ratio theory, a mathematical model of the relationship between rock damage and AE numbers was established to study the rock damage process and the precursor of rock failure. The results showed that acoustic emission principles can reflect the rock damage process. Under cyclic loading, rock damage increases with stress level during the unload phase, but the Y value of acoustic emission load/unload ratio decreases gradually. For most rock specimens, the Y value reaches 1 and fluctuates in a small range when rocks reach the later phase of elastic deformation, which can be seen as a precursory characteristic to rock failure and this is meaningful to the forecasting of rock unstable failure under cyclic loading.