Abstract: According to the internal forces and the deformation characteristics of members under axial compression, rectangular hollow variable cross-section braces were proposed. The elasto-plastic stability behaviors as well as the effect of the wedge rate on the ultimate bearing capacity were investigated by the experimental and finite element method. Compared to the constant cross-section braces with the same steel quantity, the stability behaviors for rectangular hollow variable cross-section braces were analyzed. Different slenderness ratios and wedge ratios were considered in the analysis to evaluate how these parameters influenced the stability behaviors. The research results show that the stability bearing capacity increases with the increase of the wedge rate if the end cross-sections of braces remain invariable. The larger the wedge ratio, the flatter the descending branch of the force-deformation curve. The rectangular hollow variable cross-section braces have a more desirable stability. If the steel consumption stays unchanged, the proposed braces with a larger slenderness ratio can have an enhanced bearing capacity and may be applied to those frame-brace systems located on a site with low seismicity. In addition, the stress performance of the brace after losing stability can be improved by taking a smaller slenderness ratio, and such a brace is suitable for high-seismicity regions.