Fatigue is a primary reason contributing to the failure of engineering structures and machines. Experiments show that rock, as a kind of natural material with a complex internal structure, exhibits a wide dispersion of experimental data in conventional static and dynamic tests. Many theories that have proved efficacious and are used widely for metals cannot be applied to rocks. For example, the fatigue damage cumulative theory is the foundation of fatigue life analysis. And, it is well known that the S2N curve is necessary to estimate the fatigue life of rock subjected to variable amplitude loading by using Miner’s linear fatigue damage cumulative theory. However, it has been deduced [1] that fatigue life N is dependent on the stress level S, and the fatigue life predicted by Miner’s rule is far from the actual value, because of the scatter of static strength. In fact, despite the fact that the Miner’s linear fatigue damage cumulative theory is used comprehensively in engineering, due to its advantage of being simple, visual and distinct, it is limited by finite calculation accuracy, especially under two-level or multilevel loadings, and for not taking loading sequence effect and loads interaction effect into account. To overcome this defect, many modified linear fatigue damage cumulative theories and nonlinear ones [2] have been proposed in the past several decades. Most of them are brought forward to solve some problems of metal materials and cannot be applied to rock directly. Therefore, two key problems must be addressed before undergoing fatigue analysis in rock mass. The first one is reasonable definition of rock damage, and the other is construction of fatigue damage cumulative model for rock.