Abstract: The rock mass in the fault zone is characterized by fissures and previous high-stress damage. To explore the mechanical property of rock mass with high-stress previous damage after excavation when a tunnel passes through a fault zone and its impact on supports, different discrete element numerical models of two unloading paths are designed: pre-peak unloading, reflecting the excavation of ordinary tunnels; post-peak unloading, reflecting the excavation of tunnels in the rock mass with high-stress previous damage in a fault zone. The calculation parameters of discrete element models are calibrated through the triaxial compression test of white sandstone samples, and then numerical calculations are conducted to compare and study the mechanical behaviors of surrounding rocks in these two unloading paths. The results show that the self-bearing capacity of the surrounding rock with high-stress previous damage collapses at a faster speed after excavation-induced unloading, so supports shall be provided more timely; the support strength required is significantly increased to achieve the identical amount of deformation of surrounding rock; and it is more difficult to support the micromechanism for the significant development of tensile microcracks.