In　order　to　study　microscopic　failure　mechanism　of　concrete　under　impact　loading,　the　concrete　is　considered　as　a　three-phase　composite　composed　of　matrix,　aggregate　and　interface　between　them.　The　number　of　aggregates　is　calculated　by　using　Walraven　J.C　formula　and　meso-scale　structure　is　represented　with　random　aggregate　model　by　using　Monte-Carlo　method.　The　bilinear　damage　evolution　model　is　adopted　to　describe　the　meso-element＇s　damage　devolution.　The　microscopic　failure　mechanism　of　concrete　under　impact　loading　is　simulated　with　nonlinear　finite　element　method,　stress-strain　curve　of　specimen　and　its　dynamic　compressive　strength　are　got.　The　results　show　that　the　numerical　solutions　are　fitted　with　experiment　results.