The　proposed　method　in　GB　50608—2020“Technical　specification　for　construction　engineering　application　of　fiber　reinforced　composites”　still　cannot　consider　the　influence　of　size　effect　and　shear-span　ratio　on　shear　capacity　of　fiber　reinforced　polymer　(FRP)　reinforced　concrete　beams.　In　this　paper,　650　groups　of　shear　capacity　experimental　data　of　FRP　reinforced　concrete　beams　(including　511　groups　of　beams　without　stirrup　and　139　groups　of　beams　with　stirrup)　were　collected.　Based　on　this,　the　gray　correlation　method　was　used　to　reveal　the　importance　of　shear-span　ratio,　structural　size,　longitudinal　reinforcement　ratio　and　stirrup　ratio　on　the　shear　capacity　of　FRP　reinforced　concrete　beams.　The　correction　coefficient　of　important　factors　(size　effect,　longitudinal　reinforcement　ratio　and　shear-span　ratio)　and　the　safety　factor　of　stirrup　ratio　were　proposed.　Combined　with　the　calculation　formula　in　GB　50608—2020,　a　new　calculation　method　of　shear　capacity　of　FRP　reinforced　concrete　beams　was　established.　The　efficiency　of　the　proposed　method　has　been　evaluated　by　comparing　the　calculated　shear　strength　with　the　experimental　data.　The　results　show　that　the　modified　calculation　formula　can　better　reflect　the　influence　law　of　shear-span　ratio,　structural　size　and　longitudinal　reinforcement　ratio,　and　has　obvious　advantages　in　terms　of　mean　value,　coefficient　of　variation　and　safety　factor.　It　can　be　used　in　the　shear　design　of　FRP　reinforced　concrete　beams.　©　2023　Science　Press.　All　rights　reserved.