<p>Due to intense geological tectonic activity, numerous cross-joints develop in deeply buried rock masses, significantly influencing their mechanical properties and failure behavior. These structural discontinuities pose considerable challenges to the stability and safety of engineering structures excavated using drilling and blasting techniques. Therefore, this study employs a Hopkinson pressure bar with confining pressure and the discrete element method (DEM) to systematically investigate the effects of cross-joints, strain rate, and confining pressure on the dynamic mechanical response and fracture behavior of granite, providing insights into the failure mechanisms of jointed rock masses under dynamic loading conditions. The findings indicate that the dynamic strength, energy transfer characteristics, and failure modes of granite are governed by the coupling effects of cross-joints and loading conditions. By analyzing acoustic emission (AE) data and displacement vector fields, this study reveals the influence of cross-joints on microcrack types, microcrack propagation directions, and failure modes. A macro–microcrack identification method is established by integrating displacement vector fields with displacement trend lines (DTLs). Furthermore, the generation mechanism and formation process of straight and vortex-shaped displacement trend lines in jointed granite specimens are elucidated. Finally, this study explains the similarities between the opening, closing, and dislocation behaviors of preexisting joints and the dislocation behaviors of fault zones in deeply buried rock masses.</p>