The reinforced concrete shear walls of nuclear power plants have a low shear span ratio and high reinforcement ratio. Multiple openings are required to allow for the introduction of doors and pipelines into the building. However, research on the seismic performance of low-rise shear walls with openings is relatively limited. Therefore, three 1∶2.7 squat reinforced concrete shear walls were experimentally investigated through quasi-static testing to analyze the impact of shear span ratio on seismic performance. The study included analysis and discussion of the failure mode, hysteresis curves, ductility coefficients, stiffness degradation, energy dissipation capacity, and deformation capacity of the specimens. The results indicated that the failure in low-rise shear walls was primarily caused by the significant increase in the width of diagonal principal cracks in the wall legs, leading to a rapid decrease in bearing capacity. Furthermore, reducing the shear span ratio increased the bearing capacity, stiffness, and energy dissipation of low-rise shear walls, but significantly reduced their deformation capacity and ultimate displacement, resulting in lower cumulative energy dissipation. Specimens with smaller shear span ratios were prone to develop plastic hinges above the openings, and subsequent beam rotation caused concrete crushing near the openings, with significant shear effects. Moreover, the presence of small openings resulted in severe asymmetry, affecting the seismic performance of the shear walls.