Abstract: Complexity of fatigue damage process of intermittence jointed rock masses subjected to dynamic loading was analyzed, and an approximate evaluation method was set forth. The process of dynamic fatigue damage accumulation was discussed based on residual strain intensity theory and linear degradation criterion. The equivalence between rupture probability and fatigue damage variable was studied using statistical method and the quantitative relation between fatigue damage variable and fractal dimension was established. Correctness of the conclusion was validated through dynamic fatigue experiments.