In general, the structural response of a shear wall depends on the type of loading, the aspect ratio of the shear wall, the size and location of openings in the shear wall, and seismic reinforcement and design around the openings. In most cases, these shear walls contain windows and utility ducts or door openings that were not included or anticipated in the original design and were created later after construction. In these cases, corrective external strengthening is required to restore the structural integrity and restore the seismic capacity and ductility of the building. This paper investigates the effects of openings with eccentricity of 0% to 20% and increasing the width and height of the openings and the effects of concrete compressive strength and the effects of reinforcing steel plates on the bearing capacity, stiffness, stress and strain in concrete and rebar of shear walls and the damage and failure modes of shear walls using the nonlinear finite element method in Abaqus software. By creating post-construction openings, the bearing capacity of the wall is reduced and its initial stiffness is also reduced. The results show that steel plates have a good performance in restoring the bearing capacity and initial stiffness of reinforced concrete shear walls with post-construction openings. After strengthening with steel plates, the ultimate bearing capacity is close to the bearing capacity of the shear wall without openings with a relative difference of 3 to 6%. After strengthening with steel plates around post-construction openings, the uneven strain distribution of the rebars around the openings is clearly improved and the strain amplitude is also reduced.