To　study　the　bending　strength　of　mass　concrete　under　dynamic　loading,　the　pure　bending　zone　of　three-graded　concrete　beam　is　considered　as　a　three-phase　composite　composed　of　matrix,　aggregate　and　interface　between　them　on　meso-level.　Dynamic　constitutive　model　considering　strain-rate　strengthening　effect　and　damage　softening　effect　is　adopted　to　describe　the　co-crete　and　meso-element＇s　damage.　The　failure　mechanisms　of　beam　under　impact　loading,　tria-gle　wave　load,　dynamic　load　coupling　with　initial　static　loading　were　simulated　by　using　displacement-controlled　FEM.　Furthermore,　stress-strain　curve　of　the　specimens　and　their　dynamic　bending　strength　were　obtained.　The　results　obtained　from　numerical　simulation　agreed　well　with　experimental　data.