In　practical　engineering,　reinforced　concrete　(RC)　beams　with　stirrups　are　the　predominant　form　of　RC　beams.　The　geometric　dimensions　of　RC　beams　are　large,　and　the　brittle　shear　failure　of　them　maybe　show　the　characteristics　of　size　effect.　However,　current　research　primarily　focuses　on　the　size　effect　of　shear　failure　in　RC　beams　without　stirrups,　with　less　emphasis　placed　on　those　with　stirrups.　Furthermore,　when　the　minimum　stirrup　ratio　is　exceeded,　there　is　no　consensus　regarding　on　whether　the　size　effect　still　exists.　Therefore,　the　objective　of　the　present　work　is　to　discover　the　influence　of　the　stirrup　ratio　on　the　size　effect　in　RC　deep　beams.　In　this　work,　the　shear　failure　experiment　of　RC　deep　beams　considering　the　structural　size　(maximum　beam　height　of　900　mm)　and　stirrup　ratio　(0%∼0.942%)　is　designed　and　completed.　The　experiment　results　indicate　that:　1)　for　the　beams　without　stirrups,　clearly,　the　corresponding　size　effect　on　the　shear　strength　is　the　most　obvious,　with　beam　depth　increases　from　300　mm　to　900　mm,　the　nominal　shear　strength　decreases　approximately　by　41%;　2)　as　the　stirrup　ratio　increases　from　0　to　0.942%,　the　size　effect　is　weakened　with　the　presence　of　stirrups;　3)　however,　size　effect　cannot　be　completely　eliminated　even　when　the　stirrup　ratio　reaches　as　high　as　0.942%;　(4)　generally,　for　the　stirrup　ratio　of　0.3%,　there　is　a　decrease　in　nominal　shear　strength　by　20%,　indicating　that　consideration　of　size　effects　should　be　taken　seriously　in　practical　concrete　structure　design;　(5)　moreover,　Jin　et　al.’s　size　effect　law　is　also　compared　and　validated　by　the　present　test　data.　©　2023　Elsevier　Ltd