Abstract: High-rise buildings are often associated with stability problems of longitudinal exterior walls in staircases. The longitudinal exterior walls, of no support, are generally connected to other parts of the building by coupling beams. In traditional structure design, the stability of the walls is often overestimated when the walls subject to transverse bending. This study investigated the stability issue of out-plane bending of longitudinal stair walls under self-weight. Firstly, a theoretical method was proposed to calculate the critical loading based on the energy principles. The theoretical results were in good agreement with the results of finite element simulation. Subsequently, a high-rise shear wall structure was taken into consideration as a case study. The results show that the instability of the rectangular longitudinal exterior wall in staircase might occur. Finally, four measures were suggested to maintain the wall stability:1) adding flanges or air shafts; 2) anchoring the distributed reinforcements of stair slabs into the rectangular wall; 3) replacing the rectangular wall with the infill wall, and 4) calculating the earthquake action without taking into account the rectangular wall. Based on the analysis results of the four measures, it has been concluded that abolishing the rectangular wall, arranging the beam at the story height, and setting the lightweight infill wall on the beam can avoid the stability issue of the rectangular wall in a staircase. This measure is easy to construct and is recommended. However, in seismic zones, improving the collapse-resistant capacity of lightweight infill walls in staircases is necessary to keep the emergency exit unimpeded.