Abstract: From the mesoscopic view, combining with the micro/mesoscopic structural character of concrete, as well as considering the nonlinear binding-slip behavior between a steel bar and concrete, a three dimensional meso-scale numerical model and the method for a reinforced concrete (RC) cantilever beam were set up. Based on the numerical method, the shear performance of a RC cantilever beam under cyclic loading was analyzed, the numerical results are well fitted with the experimental results, and it shows the feasibility of the mesoscopic numerical method. Then on this basis, the shear-failure process of different stirrup-ratio-RC cantilever beams is further simulated, and the influence regularity of stirrup on hysteretic characteristic and the shear bearing capacity of a cantilever beam are revealed. The research shows that:1) the mesoscopic numerical model can better simulate the mechanical properties, and it can detailed describe the development process of cracks in concrete; 2) with the increase of stirrup ratio, shear-bearing capacity and ductility increase, but with the increase of stirrup ratio, the increasing trend of RC-beam-shear-bearing capacity slow down gradually. The meso-scale numerical method can provide a theoretical support for the shear/bend size effect of beams with/without web reinforcement.