The appearance of openings in beams is considered inevitable for structures that require aesthetic considerations, where the clear height of the floor is limited, and the arrangement of suspended ceilings as well as complex spatial layouts is necessary. Openings will cause many inconveniences for the behavior of typical beam systems such as deformation, load-bearing capacity, and stability. In the context of Vietnam, with the trend of renovating building spaces, openings often appear after the design has been completed, so understanding how the behavior of beams changes when openings appear is very necessary. This paper analyzes the behavioral changes of beams when openings appear, as well as the impact of various reinforcement methods around the openings by the simulation of ABAQUS. The research results show that openings located within the shear span of the beam significantly reduce the load-bearing capacity and deformation of the beam. The most effective reinforcement option when there is an opening is the option that includes diagonal reinforcement bars around the opening. Vertical stirrups around the opening provide little improvement in the behavior of beams with openings.