In　order　to　explore　the　similarities　and　differences　of　shear　performance　and　size　effect　between　BFRP-reinforced　concrete　deep　beams　and　RC　deep　beams,　numerical　tests　on　static　shear　failure　of　BFRP-reinforced　concrete　deep　beams　and　RC　deep　beams　were　carried　out　by　using　three-dimensional　mesoscopic　numerical　method.　Based　on　the　existing　tests,　the　rationality　and　accuracy　of　the　simulation　method　were　verified.　The　effects　of　beam　heights,　shear　span-to-depth　ratios　and　reinforcement　types　(BFRP　bars　and　steel　bars)　on　shear　failure　behavior　and　corresponding　size　effect　of　deep　beams　were　analyzed.　In　addition,　the　simulation　results　were　compared　with　those　calculated　based　on　national　codes　and　the　size　effect　law　proposed　by　Jin　et　al.　The　results　show　that:　1)　The　shear　size　effect　of　BFRP-reinforced　concrete　deep　beams　is　more　evident　than　that　of　RC　deep　beams,　that　is,　as　the　cross-section　height　increases,　the　shear　capacity　and　ductility　of　BFRP-reinforced　concrete　deep　beams　may　decrease　more　markedly　than　those　of　RC　deep　beams;　2)　The　shear　span-to-depth　ratio　may　significantly　affect　the　shear　strength　of　beams,　but　barely　influence　the　shear　size　effect　of　beams;　3)　For　the　shear　capacity　of　large-size　beams,　the　safety　reserve　of　results　calculated　from　the　codes　in　different　countries　may　not　be　enough,　and　in　these　codes　the　shear　span-to-depth　ratio　may　not　be　considered　for　FRP-reinforced　beams;　4)　The　size　effect　law　proposed　by　Jin　et　al.　shall　also　be　applicable　to　concrete　deep　beams　with　BFRP　bars　and　steel　bars.　©　2022　Editorial　Office　of　China　Civil　Engineering　Journal.　All　rights　reserved.