To study the size effect of shear strength of recycled concrete beams without web reinforcement, a group of physical tests are carried out under the condition of a constant shear span ratio. The results show that the shear strength of the test beam generally decreases with the increase in beam section height, and a regression formula of the shear strength is obtained, which can quantify this effect. The rationale and feasibility of the explicit finite element method solving the ultimate load of concrete structures are briefly demonstrated, and an explicit finite element simulation of test beams is carried out. The results show that an obvious and phenomenologically regular size effect of the shear strength of recycled concrete beams without web reinforcement, which can be better simulated by the explicit finite element method.