Abstract: This study investigates the evolution of mechanical stability in granular materials during shear, within the framework of the second-order work criterion using the DEM. A meso-scale second-order work is developed using meso-loop structure as the fundamental analysis units, aiming to reveal the distinct stability characteristics inside and outside the shear band, as well as the contribution of different loop types to both local and global stability. The results show that, the negative value of the macroscopic second-order work of the dense specimen appears at the peak stress state with the initial formation of shear band, indicating a bifurcation from a stable to an unstable state. As shearing progresses, the instability of loop intensifies significantly, leading to the spatial concentration of localized failure. In contrast, the domain outside the shear band retains a high level of stability throughout. The evolution of second-order work within the shear band closely aligns with that of the whole specimen, suggesting that the global instability is predominantly governed by localized instability within the shear band. Moreover, distinct differences in stability are observed among loop types: 3-cycle loops exhibit higher stability, while 4-cycle, 5-cycle, and especially high-order 6+-cycle loops are more prone to instability. The synchronized destabilization of these higher-order loops can further amplify local instabilities within the shear band, ultimately triggering global structural failure.