Hydraulic　fracturing　is　widely　used　in　the　exploitation　of　unconventional　gas　(such　as　shale　gas).Thus,　the　study　of　hydraulic　fracturing　is　of　particular　importance　for　petroleum　industry.　The　combined　finite-discrete　element　method　(FDEM)　proposed　by　Munjiza　is　an　innovative　numerical　technique　to　capture　progressive　damage　and　failure　processes　in　rock.　However,　it　cannot　model　the　fracturing　process　of　rock　driven　by　hydraulic　pressure.　In　this　study,　we　present　a　coupled　hydro-mechanical　model　based　on　FDEM　for　the　simulation　of　hydraulic　fracturing　in　complex　fracture　geometries,　where　an　algorithm　for　updating　hydraulic　fracture　network　is　proposed.　The　algorithm　can　carry　out　connectivity　searches　for　arbitrarily　complex　fracture　networks.　Then,　we　develop　a　new　combined　finite-discrete　element　method　numerical　code　(Y-flow)　for　the　simulation　of　hydraulic　fracturing.　Finally,　several　verification　examples　are　given,　and　the　simulation　results　agree　well　with　the　analytical　or　experimental　results,　indicating　that　the　newly　developed　numerical　code　can　capture　hydraulic　fracturing　process　correctly　and　effectively.