<p>Blasting excavation and mechanical excavation cause unloading damage of surrounding rock. To study the damage pattern caused by different excavation unloading of rock mass, a triaxial test system was used to carry on quasi-static and transient unloading tests on granite and sandstone. Acoustic emission systems were used to monitor the fracture signal of rock in unloading. Experiment results show that the unloading decline of granite stress–strain curve is more pronounced compared to sandstone. Both quasi-static and transient unloading tests, with stress load increased continuously, acoustic emission energy activity increase. When the rock reached unloading stage, the acoustic emission energy activity decrease. Both granite and sandstone perform spalling in quasi-static and transient unloading tests, with the failure mode is tensile splitting failure, and sandstone also perform shear failure crack. Transient unloading led to rock perform many tensile fractures and apparent spalling compared to quasi-static unloading. Comparing specimen failure result with rock mass failure phenomena in underground engineering such as rock bursts. Under high in-situ stress condition, rock mass in quasi-static unloading may cause rock spalling, while in transient unloading can cause more rock spalling. The quickly release of stored energy from weak zones in the rock mass may potentially lead to dynamic disaster.</p>