A　three-dimensional　mesoscale　numerical　analytical　model　for　studying　CFRP　reinforced　RC　beams　was　developed　using　the　ABAQUS　finite　element　numerical　calculation　platform.　The　heterogeneity　of　concrete　material　and　the　interaction　between　rebar/CFRP　and　concrete　was　considered.　Different　strain　rates　were　studied　to　explore　the　size　effect　behaviors　and　shear　failure.　The　conclusions　show　that:　1)　with　the　increase　of　the　strain　rate,　the　shear　bearing　capacity　increases,　and　with　the　increase　of　the　beam　height,　the　nominal　shear　strength　decreases;　2)　increased　strain　rate　can　result　in　RC　beams　reinforced　with　CFRP　having　greater　nominal　shear　strength,　while　it　can　also　result　in　diminished　size　effect　behaviors;　3)　the　nominal　shear　strength　was　predicted,　a　formula　that　considers　both　the　size　effect　and　the　strain　rate　effect　was　proposed.　©　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd　2024.