<p>Cyclic shear loading facilitates complex fracture network formation and enhances geothermal resource exploitation. Systematic cyclic direct shear (CDS) experiments with real-time acoustic emission (AE) and digital image correlation (DIC) monitoring were conducted on granite to investigate its progressive failure behavior. The results indicate that the shear strength, strain, modulus, and energy parameters of granite exhibit nonlinear and non-monotonic evolutionary trends, responding differently to increasing shear cycle number. Moreover, normal stress plays a dominant role in controlling asymmetric crack propagation, surface roughening, and shear strength. In the pre-peak stage, granite displays high shear modulus due to elastic deformation and energy storage. A transition to plastic deformation and accelerated damage development occurs in the post-peak stage. With increasing shear cycle number, the AE response shows increased activity and amplitude, while DIC-measured strain exhibits a significant rise. Felicity ratio, <i>b </i>value, and peak frequency decrease significantly and stabilize after the peak. These trends reflect a transition from microcracks to macrocrack coalescence and multi-surface rupture. With increasing normal stress, the proportion of shear AE events decreases, while tensile AE signals localize near the shear plane, indicating tensile cracking and shear band formation. The nonlinear, asynchronous evolution of the cohesion and friction angle indicates that the differential release of elastic and dissipative energy is the dominant mechanism of shear failure, which controls crack nucleation, propagation, and complete failure. A shear strength model incorporating the effects of normal stress and shear strain was established, which can predict the real-time shear strength of granite.</p>