The　interface　transition　zone　(ITZ)　has　a　significant　impact　on　the　concrete＇s　mechanical　properties　and　fracture　modes.　For　the　influence　of　ITZ＇s　strength　and　elastic　modulus,　the　extended　finite　element　method　(XFEM)　is　adopted　to　simulate　the　mesostructure　failure　process　by　virtue　of　random　aggregate　model　under　uniaxial　tension.　The　results　show　that　ITZ＇s　strength　and　elastic　modulus　have　a　certain　effect　on　the　mechanical　properties　and　fracture　modes.　With　the　tensile　strength　of　ITZ　increasing,　the　fractured　modes　transit　from　single　coalescent　crack　to　multiple　non-coalescent　cracks　and　the　fracture　energy　increases,　the　ductility　of　concrete　is　enhanced.　With　the　elastic　modulus　of　ITZ　increasing,　the　concrete＇s　elastic　modulus　increases,　the　tensile　strength　and　the　fracture　energy　decrease.