Hydraulic　fracturing,　which　determines　geothermal　resource　productivity,　is　one　of　the　critical　technical　components　in　the　construction　of　hot　dry　rock　(HDR)　reservoirs.　Although　the　mechanical　coupling　between　solid　and　fluid　has　been　included　in　algorithms　based　on　the　discrete　element　method　(DEM)　generally　employed　to　investigate　hydraulic　fracturing,　crystalline　rocks　of　reservoirs　are　mostly　treated　as　homogeneous　isotropic　models　without　considering　their　petrographic　texture.　By　combining　a　grain-based　model　(GBM)　and　a　modified　fluid-solid　coupling　algorithm,　a　novel　hydro-GBM　is　constructed　in　this　study　to　analyze　the　hydraulic　fracturing　response　of　polycrystalline　rocks.　Moreover,　acoustic　emission　(AE)　events　during　fracturing　are　extracted　to　describe　the　characteristics　of　hydraulic-fracturing-induced　seismicity.　Under　in-situ　conditions　with　high　differential　stress,　the　propagation　direction　of　hydraulic　fractures　is　mainly　perpendicular　to　the　direction　of　minimum　in-situ　stress,　with　little　influence　by　material　heterogeneity　and　fluid　viscosity;　under　near-hydrostatic　in-situ　stress　conditions,　the　microcracks　along　the　mineral　boundaries　increase　remarkably,　and　the　fracture　pattern　tends　to　be　complex,　especially　when　a　low-viscosity　fluid　is　injected　into　the　rock.　From　the　Gutenberg-Richter　type　relationship　between　the　AE　event　numbers　and　the　moment　magnitudes,　it　is　found　that　large　induced　seismic　events　increase　with　in-situ　stress　and　with　fluid　viscosity.　In　summary,　the　proposed　hydro-GBM　can　well　reproduce　the　propagation　behavior　of　hydraulic　fractures　influenced　by　material　heterogeneity,　and　the　research　results　reveal　the　interactions　between　petrographic　texture,　in-situ　stress,　fluid　viscosity,　and　hydraulic　fracturing　characteristics,　which　will　provide　a　valuable　reference　for　on-site　reservoir　stimulation.