In this paper, three existing models for calculating the shear strength of the core of beam-column joint are introduced and analyzed. Calculated results show that the theoretical results do not match experimental results, with considerable dispersion. Based on the strut and truss model, a modified model is proposed, in which a softening coefficient of cracked concrete and a correction coefficient for high concrete joints are considered. Results of the modified model are close to experimental results, and are safe. The modified model can be applied to normal and high strength reinforced concrete joints.