<p>Rock engineering often suffers shear fatigue failure due to cyclic dynamic disturbances, which could be of constant or variable amplitude. However, the fatigue behaviors of rock subjected to cyclic dynamic shear have not been fully clarified. To systematically investigate rock dynamic shear fatigue properties, cyclic dynamic shear experiments, in which the impacts are constant or variable, were performed on granite via the split Hopkinson pressure bar. Experimental results showed that under constant and variable amplitude cyclic loading, the peak shear stress and shear stiffness of granite decrease while the peak shear displacement increases as the number of impacts increases. The fatigue threshold of granite under constant amplitude cyclic shear is 0.68 times the critical impact stress at which it fails in a single impact. With the decrease in impact stress, the fatigue life and total dissipated energy of granite increase, and the shear fracture surface becomes rough. The fatigue damage development of granite under constant amplitude cyclic loading exhibits a three-stage characteristic, including rapid growth in the initial stage, stable development in the middle stage, and accelerated accumulation in the final stage. For variable amplitude cyclic shear loading, applying high amplitude loads earlier to the granite correlates to a quicker rock damage accumulation and shorter fatigue life. Moreover, the mesoscopic observation reveals that the full development of the intergranular cracks and the gradual fragmentation of grains are the primary fatigue mechanisms. These findings promote better understanding of rock dynamic fatigue behavior.</p>