Fracture　structure　in　the　rock　mass　is　an　enduring　research　interest　because　of　its　negative　impacts　on　the　strength　and　safety　of　rocks.　Therefore,　a　series　of　DEM　simulations　of　two　types　of　fractured　sandstones　are　conducted　based　on　the　former　published　experimental　test.　It　is　proved　that　different　fracture　structures　have　various　influences　on　the　mechanical　properties　and　failure　patterns　of　sandstone　samples,　which　lead　to　the　redistribution　of　principal　stress　in　surrounding　rock.　The　main　results　and　conclusions　are　as　follows:　1)　fractured　sample　without　filler　shows　a　relatively　lower　uniaxial　compressive　strength　and　a　larger　elastic　modulus,　and　the　flaw　free　surfaces　make　the　secondary　crack　band　illustrate　a　typical　arc-shape　distribution.　2)　maximum　principal　stress　concentrations　in　the　open-type　flawed　sample　occur　at　the　left　and　right　flaw　tips,　the　corresponding　axes　show　progressive　deflection　in　the　vertical　direction,　and　the　intermediate　and　minimum　principal　stress　axes　demonstrate　various　rotations　as　the　positions　move　away　from　the　flaw　tip.　3)　maximum　principal　stress　axes　in　the　cement-filled　fractured　sample　are　basically　parallel　to　the　external　loading　direction,　the　largest　deflection　occurs　in　the　cement　filler　material,　and　the　intermediate　principal　stress　axes　near　the　flaw　tip　are　consistently　vertical　to　the　flaw　strike　direction.　4)　initiation　positions　of　tensile　and　shear　cracks　in　the　opentype　flaw　sample　are　different　because　of　the　non-negligible　flaw　thickness,　while　all　secondary　cracks　start　from　the　top　and　bottom　tips　of　the　cement-filled　flaw.