The shear capacity formula for deep flexural members in Appendix G of GB/T.50010-2010 Code for Design of Concrete Structures , namely the GB/T50010 formula, does not account for the influence of openings and thus cannot be accurately applied to the design of deep beams with square openings. To address this issue, the calculation method for the shear capacity of deep beams with square openings was investigated. Based on the statistical analysis of relevant test data to evaluate the reliability of the traditional method, the ultimate bearing capacity of nine groups of members was compared through nonlinear finite element simulation. The influence of opening parameters on the force performance was analyzed. At the same time, the modified formula of the GB/T50010 formula was given by using the fitting method, and the applicability of the modified formula was verified. The results indicate that the traditional empirical reinforcement method, which involves adding additional reinforcement around openings, lacks sufficient reliability. For a deep beam with square openings, the reduction in shear capacity is primarily governed by the opening position and opening ratio. Specifically, shorter vertical distances from the opening centroid to the compressive path (i.e., the line connecting the loading point and the support) and a larger opening ratio correlate with a decrease in the member’s shear capacity. Moreover, the opening behavior mainly reduces the contribution of concrete to the shear capacity of the member; the modified formula, by adjusting the concrete’s shear contribution term, can fully consider the adverse effects of single or double openings. Within a defined range of opening sizes and positions, the modified formula significantly improves the prediction accuracy of the shear capacity of a deep beam with openings.