Six　reinforced　concrete　short　columns　under　low　cycle　reversed　loading　and　monotonic　horizontal　loading　were　tested　to　investigate　the　size　effect　on　shear　behavior　of　columns.　The　analysis　results　show　that　the　safe　coefficient　of　shear-bearing　capacity　decrease　as　section　size　increase.　The　theory　of　truss-arch　model　was　applied　to　the　analysis　of　the　shear　mechanism　of　reinforced　concrete　short　columns,　then　it　was　concluded　that　the　size　effect　of　shear-bearing　capacity　is　generated　by　concrete,　and　a　practical　calculation　model　of　shear-bearing　capacity　of　reinforced　concrete　column　considering　section　size　effect　coefficient　was　proposed.　The　results　indicate　that　the　safety　coefficient　of　large　size　specimen　is　consistent　with　results　of　small　size　specimen　when　the　section　size　effect　is　considered.