Opening in the web of reinforced concrete (RC) beams will destroy the integrity of the beam and weaken the mechanical properties of the RC beam, such as the bearing capacity and stiffness. The three-point loading test and finite element analysis were carried out on 10 RC beams with a huge rectangular opening in the web. The effects of stirrups around the holes on the shear properties of RC opening beams, such as bearing capacity, deformation capacity, and stirrup strain, were studied, and the shear transfer mechanism of RC beams at the openings was explained by using the strut-and-tie model. The finite element test results are consistent with the actual test results, as shown by the results. When the hole width is small, the reinforcement of stirrups at the hole side can significantly improve the shear capacity of the specimen, but it can also cause chord shear failure. When the hole height is small, with the strengthening of the chord stirrup, the ultimate bearing capacity of the specimen increases, but it can still result in hole-side shear failure. The curve of stiffness degradation is approximately logarithmic. Moreover, according to the finite element stress vector diagram, the shear transfer mechanism of the perforated beam based on the strut-and-tie model has been proved.