In　engineering　construction,　the　presence　of　internal　fissures　in　rock　masses　and　the　accumulation　of　internal　energy　are　the　main　factors　affecting　rock　failure.　To　study　the　effects　of　fissures　and　borehole　pressure　relief　on　rock　masses　separately,　this　paper　has　prepared　various　drilling　samples　with　different　fissures　in　the　laboratory.　On　the　basis　of　maintaining　the　original　number　of　fissures,　new　fissures　and　holes　are　added　to　explore　their　effects　on　the　rock　mass.　Combined　with　discrete　element　numerical　simulation,　the　microscopic　characteristics　of　multi-fissure　samples　and　borehole　samples　are　analyzed.　The　research　results　indicate　that　as　the　fissure　dip　angle　increases,　failure　occurs　gradually　along　the　existing　fissures,　while　the　crack　development　in　the　borehole　samples　is　mainly　concentrated　around　the　holes,　and　the　boreholes　have　a　greater　impact　than　fissures.　The　study　of　the　change　rule　and　damage　characteristics　of　the　fissures　before　and　after　drilling　of　multi-fissure　specimens　can　provide　a　reference　for　controlling　the　deformation　of　the　rock　mass　in　engineering　applications.