The　macroscopic　mechanical　properties　of　concrete　are　highly　related　to　its　internal　mesoscopic　composition.　This　paper　presents　a　theoretical　prediction　model　of　concrete　macroscopic　mechanical　properties　considering　the　mesoscopic　composition.　Firstly,　the　parameters　in　the　theoretical　model　are　calibrated　by　meso-scale　numerical　tests.　Then,　the　size　effect　of　the　concrete　fracture　energy　and　the　uniaxial　tensile　strength　in　material-level　is　analyzed　based　on　the　proposed　model.　The　results　show　that　the　concrete　fracture　energy　and　the　uniaxial　tensile　strength　both　vary　with　the　aggregate　gradation　(i.e.　the　maximum　aggregate　size),　and　they　are　also　influenced　by　the　characteristics　of　aggregate-matrix　interface.　When　the　aggregate-matrix　interfaces　are　weak,　the　concrete　strength　is　low,　and　the　concrete　fracture　energy　and　the　uniaxial　tensile　strength　both　decrease　with　the　increase　of　the　aggregate　gradation.　When　the　aggregate-matrix　interfaces　are　relatively　strong,　the　concrete　strength　is　high,　and　the　concrete　fracture　energy　and　the　uniaxial　tensile　strength　both　increase　with　the　increase　of　the　aggregate　gradation.　The　calculation　results　are　in　good　agreement　with　the　test　results　and　verify　the　accuracy　and　rationality　of　the　theoretical　prediction　model　established　in　this　paper.　©　2019,　Engineering　Mechanics　Press.　All　right　reserved.