Abstract: 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.