The　shear　failure　of　the　core　zone　of　reinforced　concrete　(RC)　beam-column　joint　has　brittle　characteristics,　so　the　size　effect　of　shear　strength　can　be　caused.　Based　on　the　existing　experimental　research　results,　the　numerical　test　method　is　used　to　analyze　the　structural　size,　axial　compression　ratio,　and　stirrup　ratio　on　the　effect　of　failure　mechanism　and　failure　mode　of　the　RC　beam-column　joint,　and　reveal　their　influence　on　the　size　effect　of　shear　strength.　The　maximum　cross-sectional　dimension　of　the　joint　is　900　mm　×　900　mm.　The　results　show　that:　(1)　under　the　monotonic　loading,　the　beam-column　nodes　exhibit　brittle　shear　failure　in　the　core　region,　and　the　nominal　shear　strength　has　a　significant　size　effect;　(2)　the　increase　in　the　axial　compression　ratio　can　enhance　the　shear　capacity　of　the　middle　joint　and　also　strengthen　the　size　effect　of　shear　strength;　(3)　an　increase　in　the　stirrup　ratio　can　increase　the　shear　capacity　of　the　joint,　but　it　can　also　weaken　the　size　effect　of　the　shear　strength.　Lastly,　the　classical　size　effect　law　proposed　by　Baant　can　reflect　the　size　effect　of　shear　failure　of　the　middle　node,　but　it　cannot　describe　the　quantitative　influence　of　the　axial　compression　ratio　and　stirrup　ratio.　©　2020,　Science　Press.　All　right　reserved.