<p>Exploring the mechanical properties and fracture characteristics of hard rocks with different water content from a mesoscopic scale can help accurately predict their deformation and failure behavior, and reduce the occurrence of engineering geological disasters in hard rocks. Granite, a typical hard rock, has been taken as the research object, and a method of constructing a 3D grain-based model of a cylindrical specimen of granite based on EBSD 2D test result image has been proposed in this article. On this basis, combined with the discrete element methods considering moisture diffusion and water-softening effects, the mechanical behavior and crack propagation characteristics of granite with different moisture contents under uniaxial compression conditions have been researched. The research results indicate that the proposed model can accurately reflect the mechanical behavior of water-bearing granite under uniaxial compression conditions. The meso-mechanical parameters of mineral particles of granite deteriorate rapidly in the initial stage of water absorption, and as the mineral particles tend to saturate, the degradation of meso-mechanical parameters gradually slows down. After the sample fails, the number of intergranular cracks is much higher than that of intragranular cracks, and intragranular cracks are mainly tensile cracks, followed by shear cracks. The number of cracks within microcline crystals is the highest, followed by bytownite and quartz, while biotite and hornblende have the lowest number of cracks.</p>