Rectangular concrete-filled tubes (RCFTs) have been widely used as columns of building and bridge piers due to several advantages such as their strength-to-size efficiency and facilitation of rapid construction. Recently, some researchers have tried to use RCFT as a wall system in a building. RCFT wall have a high aspect ratio while the aspect ratio of the RCFT column is usually one. Thus, the behavior of the RCFT wall is clearly different from that of RCFT column and it needs to be investigated. In this study, the axial behavior of the RCFT wall was investigated through analytical simulation, and the effects of the aspect ratio, internal stud, and through rebar on axial behavior of the RCFT wall were examined. From the results, it was found that axial load capacity is decreased with increasing aspect ratio due to local buckling of the steel tube, and this local buckling can be efficiently prevented by using internal through rebar.