Underground water-sealed caverns are usually excavated in granite and other hard rock masses where defective geological structures such as faults and joints develop well. In an attempt to investigate into the influence of fault fracture zone on the stability of underground cavern, we examined the displacements of surrounding rock and typical sections in FLAC^3D with varying distance between fault fracture zone and cavern. The conclusions are as follows: (1) The location of fault fracture zone has great influence on the stability of surrounding rock of adjacent side wall, but has little influence on the stability of surrounding rock of distant side wall; (2) When the distance between fault fracture zone and cavern exceeds half of the cavern span, the influence of fault fracture zone on the stability of surrounding rock can be neglected. The conclusions are of guiding importance for determining the safe distance and selecting the location of such caverns.