The surrounding rock of large underground engineering projects is often composed of hard rock, and defects such as mineral particles and micro-cracks in the hard rock, significantly affect the mechanical properties of the rock. To investigate the influence of micro-crack distribution on the mechanical behavior, damage evolution, and fracture mechanism of rock, a numerical simulation model of basalt with single crack was established using the particle flow code PFC2D, based on the widely distributed cryptocrystalline basalt in the Baihetan Hydropower Station. In this study, the laws of crack initiation, propagation, and connection in the basalt under loading were deeply studied; the influence of different crack angles on the deformation and strength of the rock mass was discussed; the evolution characteristics and fracture mechanism of the whole process of the basalt under different confining pressures were revealed. The results of this study are significant for further studies into the mechanical properties characterizing fissured rock masses, as well as providing guiding principles for the design of cavern support.