The　purpose　of　this　study　is　to　investigate　the　size　effect　on　dynamic　shear　failure　of　deep　concrete　beams　with　Basalt　Fiber　Reinforced　Polymer　(BFRP)　bars.　In　order　to　accurately　simulate　dynamic　shear　failure　behavior　of　BFRP-reinforced　concrete　deep　beams,　a　three-dimensional　meso-scale　numerical　model　was　established,　which　considered　the　heterogeneity　of　concrete,　the　interaction　between　concrete　and　BFRP　bars,　and　the　strain　rate　effect　of　meso-components.　Firstly,　the　measured　data　of　the　existing　experiments　were　input　into　the　numerical　model　to　obtain　ideal　numerical　calculation　results,　which　proved　the　rationality　and　accuracy　of　the　simulation　method.　Then,　the　shear　failures　of　geometrical-similar　BFRP-reinforced　concrete　deep　beams　with　different　sizes　under　different　strain　rates　were　studied.　The　influence　of　beam　depth,　stirrup　ratio　and　strain　rate　on　the　shear　failure　of　BFRP-reinforced　concrete　deep　beams　and　the　corresponding　size　effect　law　were　investigated.　The　results　indicate　that:　1)　The　failure　modes　of　beams　under　dynamic　loading　are　different　from　those　under　static　loading;　2)　Both　the　strain　rate　and　the　stirrup　rate　can　effectively　improve　the　bearing　capacity　of　the　beam　and　weaken　the　shear　size　effect,　but　the　effect　of　strain　rate　is　significantly　greater　than　that　of　stirrup　rate.　In　addition,　a　size　effect　law　which　can　quantitatively　describe　the　effects　of　strain　rate　and　stirrup　ratio　on　BFRPreinforced　concrete　deep　beams　was　established.　Finally,　the　size　effect　law　was　verified　by　the　simulation　results　and　the　existing　experimental　results.