Abstract: Acoustic emission (AE) characteristics of a sandstone sample in fatigue failure process were analyzed by AE testing and its fatigue damage evolution rule was studied. Based on the AE characteristics and the damage evolution rule, in consideration of the three-stage rule of irreversible deformation development of rock, the whole fatigue process can he divided into four stages. Fatigue damage failure of rock has the burst characteristic, and the damage accelerates to evolve in the failure stage. Experiment results show that, if rock's fatigue failure is monitored and forecasted by AE, it enters into the failure stage when the damage amount is about 0.4 and into the disabled stage when the damage amount is about 0.3, respectively.