To address the slabbing-buckling instability of deep roadway sidewall rock mass with vertical joints, the damage evolution law and buckling fracture instability mechanism of vertically through parallel multi-jointed rock mass were investigated under cyclic dynamic loading. Using RFPA2D numerical software, three numerical models of intact, two-jointed and four-jointed rock specimens were established. Cyclic loading-unloading simulation tests were carried out under the coupling condition of an initial vertical in-situ stress of 50 MPa and equal-amplitude cyclic loading ranging from 50–90 MPa. The shear stress fracture nephogram, acoustic emission (AE) damage characteristics, cyclic stress-strain behavior, Poisson’s ratio, and cyclic evolution laws of mesoscopic element stress and displacement were systematically analyzed. The results indicate that rock damage is significantly aggravated with the increase of loading cycles and joint quantity; the four-jointed specimen suffers the earliest damage and the most severe fracture. For jointed rock mass, AE damage presents three stages: initial plastic compaction, intermediate stable plastic damage and late brittle fracture, with cumulative AE damage increasing nonlinearly, while that of intact rock grows linearly. Compared with the intact specimen, the final cumulative AE damage of two-jointed and four-jointed specimens increases by 2.98 times and 5.20 times respectively. With the rise of cycle number, cyclic stress-strain curves shift rightward and evolve from dense to sparse, accompanied by continuous accumulation of plastic residual deformation. The loading and unloading strain of jointed rock increases nonlinearly in a slow-to-fast pattern, and elastic strain drops abruptly when buckling instability occurs; by contrast, the strain of intact rock grows linearly and steadily. Poisson’s ratio remains stable at around 0.15 before damage, and increases sharply for jointed rock in the damage and fracture stage. Joint sets significantly control the stress transfer and deformation coordination of rock elements. Stress weakening and displacement mutation appear at joint surfaces, which hinder stress propagation, weaken the deformation compatibility of rock slabs, induce stress concentration and deformation incompatibility, and further accelerate the cumulative damage of rock slabs. This study reveals the coupled damage and buckling fracture instability mechanism induced by initial in-situ stress, cyclic loading and vertical through joints. It is confirmed that vertical joints divide the rock mass into slab-like structures and amplify stress concentration, which accelerates the deterioration of rock mechanical properties and eventually causes buckling fracture instability of vertical rock slabs. The research achievements can provide a theoretical basis and numerical reference for surrounding rock stability evaluation and disaster prevention in deep underground engineering.