The　global　mechanical　behavior　of　concrete　is　determined　by　its　meso-/micro-scopic　components.　Concrete　is　regarded　as　a　three-phase　composite　composed　of　aggregate,　mortar　matrix　and　interfacial　transition　zone　(i.e.　ITZ)　herein.　It　is　assumed　that　the　aggregate　is　elastic,　which　would　not　be　damaged,　and　the　plasticity　damaged　model　combined　with　the　material　strain-rate　effect　is　employed　to　describe　the　mechanical　properties　of　mortar　matrix　and　the　ITZ.　To　investigate　the　effect　of　the　ITZ　mechanical　properties　on　the　dynamic　mechanical　properties　of　concrete,　a　flexural-tensile　sample　of　concrete　beam,　a　double-edged　notched　concrete　sample　under　uniaxial　tension　and　a　concrete　sample　subjected　to　uniaxial　compression　are　employed.　The　numerical　results　indicate　that　the　mechanical　properties　of　the　ITZ　have　an　obvious　influence　on　the　failure　mode　and　mechanical　properties　of　concrete　subjected　to　a　lower　loading　rate.　However,　when　the　loading　rate　is　very　high　(such　as　impact　load　whose　nominal　strain　rate　is　larger　than　50/s),　the　corresponding　dynamic　failure　modes　and　the　macroscopic　mechanical　properties　of　concrete　are　almost　not　affected　by　the　mechanical　properties　of　ITZ.